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: NTien Fong Chee <tien.fong.chee@intel.com>
Reviewed-by: NTom Rini <trini@konsulko.com>