sm8x50: Make mmc-sdcard the default boot device

UFS driver for sm8550-hdk is broken upstream. So we switch
to using mmc-sdcard as the default boot device for now.

Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Change-Id: I14ff8003e9e99faa77ed95f277055c40692a3ada
1 file changed