Update platformio.ini comments

Clarify flash size settings, fix old comment regarding build_flags

code/platformio.ini

@@ -38,25 +38,33 @@ platform_latest = espressif8266@2.4.0
 
 # ------------------------------------------------------------------------------
 # FLASH SIZE:
-#   configurations for 512k/1m/... ESP's are different because we use Linker Scripts to adjust flash split
-#    board_512k, ldscript_512k ( 512 KB) =  487 KB sketch,  4 KB eeprom, 16 KB reserved
-#    board_512k, ldscript_1m0m (1024 KB) =  999 KB sketch,  4 KB eeprom, 16 KB reserved
-#    board_512k, ldscript_2m1m (2048 KB) = 1019 KB sketch, 16 KB eeprom,  992 KB spiffs, 16 KB reserved
-#    board_512k, ldscript_4m1m (4096 KB) = 1019 KB sketch, 16 KB eeprom,  992 KB spiffs, 16 KB reserved, 2048 KB empty/ota?
-#    board_512k, ldscript_4m3m (4096 KB) = 1019 KB sketch, 16 KB eeprom, 3040 KB spiffs, 16 KB reserved
+#   board and ldscript must specify real flash size of the device.
+# NOTES:
+#   fs space is not used right now.
+#   SPIFFS_SUPPORT=1, FS_SUPPORT=1 will have no effect.
+#   to avoid issues with OTA process, ensure that board & ldscript match (or less than) real flash size of the device.
 # ------------------------------------------------------------------------------
+
+# 487 KB sketch,  4 KB eeprom, 16 KB reserved, no space for ota
 board_512k = esp01
 ldscript_512k = eagle.flash.512k0m1s.ld
 
+# 999 KB sketch,  4 KB eeprom, 16 KB reserved
 board_1m = esp01_1m
 ldscript_1m = eagle.flash.1m0m1s.ld
 
+# 1019 KB sketch, 16 KB eeprom,  992 KB fs, 16 KB reserved
 board_2m = esp_wroom_02
 ldscript_2m = eagle.flash.2m1m4s.ld
 
+# 1019 KB sketch, 16 KB eeprom,  992 KB fs, 16 KB reserved, 2048 KB empty/ota
 board_4m = esp12e
 ldscript_4m = eagle.flash.4m1m4s.ld
 
+# OPTIONAL:
+# 1019 KB sketch, 16 KB eeprom, 3040 KB fs, 16 KB reserved
+# ldscript_4m = eagle.flash.4m3m4s.ld
+
 # ------------------------------------------------------------------------------
 # GLOBAL BUILD FLAGS:
 #