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
diff --git a/sm8x50/sm8x50.mk b/sm8x50/sm8x50.mk
index d48f645..8272cdf 100644
--- a/sm8x50/sm8x50.mk
+++ b/sm8x50/sm8x50.mk
@@ -18,7 +18,7 @@
 $(call inherit-product, device/linaro/dragonboard/sm8x50/device.mk)
 
 #Boot from mmc-sdcard
-TARGET_SDCARD_BOOT ?= false
+TARGET_SDCARD_BOOT ?= true
 
 # Product overrides
 PRODUCT_NAME := sm8x50