Add CONFIG_SUPPORT_EMMC_BOOT flag

Match the mmc command support with Enterprise. Used as part of the
factory test

Test: build, flash, run u-boot => mmc partconf 0
Change-Id: I3bfb0b62c5366ffad938c015cccba04ecf6c1149
diff --git a/configs/mt8516_coral_defconfig b/configs/mt8516_coral_defconfig
index fa1a3a7..c1ef61b 100644
--- a/configs/mt8516_coral_defconfig
+++ b/configs/mt8516_coral_defconfig
@@ -88,3 +88,4 @@
 CONFIG_CMD_SOURCE=y
 CONFIG_MISC_INIT_R=y
 CONFIG_CMD_USB_MASS_STORAGE=y
+CONFIG_SUPPORT_EMMC_BOOT=y