[U-Boot] Should MMC drivers use CONFIG_BLK?

Hi Simon,

I was not following the changes in MMC drivers added by you.

Recently, I had some time to check those updates and convert my driver (drivers/mmc/uniphier-sd.c).

If migration is completed, MMC drivers should use CONFIG_DM_MMC_OPS CONFIG_BLK

correct?

I want to be sure if I am getting along with your DM improvement plan.