Disable MQTTsetMQTT and MQTT_HTTPS_FW_UPDATE to allow OTA for Avatto (#1046)

* Disable MQTTsetMQTT and MQTT_HTTPS_FW_UPDATE to allow OTA for Avatto Bakery IR

Trying to update my Avattos with the currently released 0.9.8 I found that OTA wasn't possible any longer as the build was now to large

0.9.8
Checking size .pio/build/avatto-bakeey-ir/firmware.elf
Advanced Memory Usage is available via "PlatformIO Home > Project Inspect"
RAM:   [====      ]  42.4% (used 34772 bytes from 81920 bytes)
Flash: [======    ]  55.2% (used 528716 bytes from 958448 bytes)

this goes back to 0.9.7, where WiFi, MQTT and firmware update was introduced over MQTT commands

0.9.7
Checking size .pio/build/avatto-bakeey-ir/firmware.elf
Advanced Memory Usage is available via "PlatformIO Home > Project Inspect"
RAM:   [====      ]  42.4% (used 34772 bytes from 81920 bytes)
Flash: [======    ]  55.2% (used 528716 bytes from 958448 bytes)

Going back to building 0.9.6 I was able to OTA update again with the much smaller build

0.9.6
Checking size .pio/build/avatto-bakeey-ir/firmware.elf
Advanced Memory Usage is available via "PlatformIO Home > Project Inspect"
RAM:   [====      ]  39.7% (used 32512 bytes from 81920 bytes)
Flash: [====      ]  41.4% (used 396804 bytes from 958448 bytes)

Building 0.9.8 with the flags brings the build back to OTAable size

0.9.8 with
	'-UMQTTsetMQTT'
	'-UMQTT_HTTPS_FW_UPDATE'
Checking size .pio/build/avatto-bakeey-ir/firmware.elf
Advanced Memory Usage is available via "PlatformIO Home > Project Inspect"
RAM:   [====      ]  39.9% (used 32684 bytes from 81920 bytes)
Flash: [====      ]  42.3% (used 405024 bytes from 958448 bytes)

Similar to the flag setting in [env:rfbridge]

I'm not even sure if MQTT_HTTPS_FW_UPDATE would even work on the Avatto, with the limited flash memory. 

Should we also add

board_build.ldscript = eagle.flash.1m64.ld

as a default, as it's required for OTA updates on the Avattos as discussed in https://github.com/1technophile/OpenMQTTGateway/issues/763#issuecomment-698864712 ?

* Doc addition for restricted MQTT options

Doc addition for https://github.com/1technophile/OpenMQTTGateway/pull/1046 and https://github.com/1technophile/OpenMQTTGateway/pull/986

docs/use/gateway.md

@@ -135,6 +135,11 @@ vEsXCS+0yx5DaMkHJ8HSXPfqIbloEpw8nL+e/IBcm2PN7EeqJSdnoDfzAIJ9VNep
 
 A bash script is available [here](ota_command_cert.zip) to simplify the use of the `server_cert` parameter.  
 
+::: warning
+The pre-built binaries for **rfbridge** and **avatto-bakeey-ir** have the above WiFi and MQTT broker credentials and the Firmware update via MQTT options disabled. This is due to the restricted available flash, so as to still be able to use OTA firmware updates for these boards.
+:::
+
+
 # State LED usage
 
 The gateway can support up to 3 LED to display its operating state:

platformio.ini

@@ -756,6 +756,7 @@ board_build.flash_mode = dout
 [env:avatto-bakeey-ir]
 platform = ${com.esp8266_platform}
 board = esp01_1m
+board_build.ldscript = eagle.flash.1m64.ld
 lib_deps =
   ${com-esp.lib_deps}
   ${libraries.irremoteesp}
@@ -767,6 +768,8 @@ build_flags =
   '-DLED_SEND_RECEIVE=4'
   '-DIR_EMITTER_GPIO=14'
   '-DIR_RECEIVER_GPIO=5'
+  '-UMQTTsetMQTT' ;We remove this function to have sufficient FLASH available for OTA, you should also use ESPWifiManualSetup and 'board_build.ldscript = eagle.flash.1m64.ld' to save flash memory and have OTA working
+  '-UMQTT_HTTPS_FW_UPDATE' ;We remove this function to have sufficient FLASH available for OTA, you should also use ESPWifiManualSetup and 'board_build.ldscript = eagle.flash.1m64.ld' to save flash memory and have OTA working
   '-DGateway_Name="OpenMQTTGateway_AVATTO_IR"'
 board_build.flash_mode = dout