configs: sama5d2_ptc_ek: read environment from FAT

On our demo setup for SD card boot, the u-boot environment
is in a FAT partition.

This patch changes the default configuration, specifing that
the u-boot environment is in a FAT partition instead of raw MMC.
Signed-off-by: NAndrei Stefanescu <andrei.stefanescu@microchip.com>
Acked-by: NEugen Hristev <eugen.hristev@microchip.com>

configs/sama5d2_ptc_ek_mmc_defconfig

@@ -32,7 +32,7 @@ CONFIG_CMD_EXT4=y
 CONFIG_CMD_FAT=y
 CONFIG_OF_CONTROL=y
 CONFIG_DEFAULT_DEVICE_TREE="at91-sama5d2_ptc_ek"
-CONFIG_ENV_IS_IN_MMC=y
+CONFIG_ENV_IS_IN_FAT=y
 CONFIG_DM=y
 CONFIG_SPL_DM_SEQ_ALIAS=y
 CONFIG_CLK=y