config: xea: Disable support for FAT file system

On the XEA (imx287) system the FAT file system is not used neither in
SPL nor u-boot proper.

Hence, to save ~6KiB of u-boot.img size - it has been disabled.

Signed-off-by: Lukasz Majewski <lukma@denx.de>
diff --git a/configs/imx28_xea_defconfig b/configs/imx28_xea_defconfig
index a174bdb..96d15e8 100644
--- a/configs/imx28_xea_defconfig
+++ b/configs/imx28_xea_defconfig
@@ -123,5 +123,4 @@
 CONFIG_SPI=y
 CONFIG_DM_SPI=y
 CONFIG_MXS_SPI=y
-CONFIG_FS_FAT=y
 # CONFIG_SPL_OF_LIBFDT is not set