env: Migrate CONFIG_ENV_IS_IN_FAT options to Kconfig

We rename the various FAT_ENV_xxx options to CONFIG_ENV_FAT_xxx so that
they can be modified via Kconfig.  Migrate all existing users to the new
values.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/am335x_evm_nor_defconfig b/configs/am335x_evm_nor_defconfig
index 49040a6..17b9f42 100644
--- a/configs/am335x_evm_nor_defconfig
+++ b/configs/am335x_evm_nor_defconfig
@@ -1,5 +1,6 @@
 CONFIG_ARM=y
 CONFIG_ARCH_OMAP2PLUS=y
+CONFIG_TI_COMMON_CMD_OPTIONS=y
 CONFIG_AM33XX=y
 CONFIG_NOR=y
 CONFIG_SPL_STACK_R_ADDR=0x82000000
@@ -50,7 +51,6 @@
 CONFIG_G_DNL_MANUFACTURER="Texas Instruments"
 CONFIG_G_DNL_VENDOR_NUM=0x0451
 CONFIG_G_DNL_PRODUCT_NUM=0xd022
-CONFIG_FAT_WRITE=y
 CONFIG_LZO=y
 CONFIG_OF_LIBFDT=y
 CONFIG_OF_LIBFDT_OVERLAY=y