u-boot is trying to make CONFIG_BLK as a hard requirement
for DM_MMC. But now it's still not.

config BLK
	bool "Support block devices"
	depends on DM
	default y if DM_MMC

When fsl_esdhc driver was reworked for DM_MMC support, DM_MMC
without CONFIG_BLK enabled wasn't considered. This patch is to
fix probe issue without CONFIG_BLK enabled.
Signed-off-by: NYangbo Lu <yangbo.lu@nxp.com>
Signed-off-by: NYinbo Zhu <yinbo.zhu@nxp.com>
Reviewed-by: NPrabhakar Kushwaha <prabhakar.kushwaha@nxp.com>