config_fallbacks: add additional fallbacks for fat filesystem

Add fallbacks needed to keep all boards building
while they are migrated to use Kconfig symbols
instead of defines in <board>_config.h files for
FAT filesystem.

These should eventually go away once Kconfig select
or imply statements are put in place and duplicated
defines in <board>_config.h removed.

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
[trini: Update logic since CMD_FAT / CONFIG_SPL_FAT_SUPPORT are
        selecting FS_FAT]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/include/config_fallbacks.h b/include/config_fallbacks.h
index 5a698a8..2656c75 100644
--- a/include/config_fallbacks.h
+++ b/include/config_fallbacks.h
@@ -29,10 +29,14 @@
 #define CONFIG_SYS_BAUDRATE_TABLE	{ 9600, 19200, 38400, 57600, 115200 }
 #endif
 
-#if defined(CONFIG_CMD_FAT) && !defined(CONFIG_FS_FAT)
+#if defined(CONFIG_ENV_IS_IN_FAT) && !defined(CONFIG_FS_FAT)
 #define CONFIG_FS_FAT
 #endif
 
+#if defined(CONFIG_ENV_IS_IN_FAT) && !defined(CONFIG_FAT_WRITE)
+#define CONFIG_FAT_WRITE
+#endif
+
 #if (defined(CONFIG_CMD_EXT4) || defined(CONFIG_CMD_EXT2)) && \
 						!defined(CONFIG_FS_EXT4)
 #define CONFIG_FS_EXT4