add IDF_ENV_FPGA option

Kconfig

@@ -4,16 +4,14 @@
 #
 mainmenu "Espressif IoT Development Framework Configuration"
 
-    # Hidden option to support checking for this specific target in C code and Kconfig files
-    config IDF_TARGET_ESP32
-        bool
-        default "y" if IDF_TARGET="esp32"
-        default "n"
-
     config IDF_CMAKE
         bool
         option env="IDF_CMAKE"
 
+    config IDF_ENV_FPGA
+        # This option is for internal use only
+        bool
+
     config IDF_TARGET
         # This option records the IDF target when sdkconfig is generated the first time.
         # It is not updated if environment variable $IDF_TARGET changes later, and
@@ -25,12 +23,10 @@ mainmenu "Espressif IoT Development Framework Configuration"
     config IDF_TARGET_ESP32
         bool
         default "y" if IDF_TARGET="esp32"
-        default "n"
 
     config IDF_TARGET_ESP32S2BETA
         bool
         default "y" if IDF_TARGET="esp32s2beta"
-        default "n"
         select FREERTOS_UNICORE
 
     config IDF_FIRMWARE_CHIP_ID
@@ -323,7 +319,7 @@ mainmenu "Espressif IoT Development Framework Configuration"
 
     menu "Compatibility options"
         config LEGACY_INCLUDE_COMMON_HEADERS
-            bool "Include headers accross components as before IDF v4.0"
+            bool "Include headers across components as before IDF v4.0"
             default n
             help
                 Soc, esp32, and driver components, the most common