spl: Kconfig: Replace CONFIG_SPL_EXT_SUPPORT to CONFIG_SPL_FS_EXT4

Replace CONFIG_SPL_EXT_SUPPORT to CONFIG_SPLY_FS_EXT4 so both
obj-$(CONFIG_$(SPL_)FS_EXT4) and CONFIG_IS_ENABLED(FS_EXT4) can be
used to control the build in both SPL and U-Boot.

Signed-off-by: Tien Fong Chee <tien.fong.chee@intel.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/arm/mach-omap2/am33xx/Kconfig b/arch/arm/mach-omap2/am33xx/Kconfig
index b144fcc..4d47d09 100644
--- a/arch/arm/mach-omap2/am33xx/Kconfig
+++ b/arch/arm/mach-omap2/am33xx/Kconfig
@@ -38,7 +38,7 @@
 	imply SPL_DM
 	imply SPL_DM_SEQ_ALIAS
 	imply SPL_ENV_SUPPORT
-	imply SPL_EXT_SUPPORT
+	imply SPL_FS_EXT4
 	imply SPL_FS_FAT
 	imply SPL_GPIO_SUPPORT
 	imply SPL_I2C_SUPPORT
@@ -232,7 +232,7 @@
 	imply DM_SPI_FLASH
 	imply SPI_FLASH_BAR
 	imply SPL_ENV_SUPPORT
-	imply SPL_EXT_SUPPORT
+	imply SPL_FS_EXT4
 	imply SPL_FS_FAT
 	imply SPL_GPIO_SUPPORT
 	imply SPL_I2C_SUPPORT