arm: sunxi: Enable DM_MMC on required SoCs

arm: sunxi: Enable DM_MMC on required SoCs

Enabling DM_MMC is forcing CONFIG_BLK=y so if any board which uses
SCSI must need to enable DM_SCSI otherwise SCSI reads on that particular
target making invalid reading to the disk drive.

Allwinner platform do support SCSI on A10, A20 and R40 SoC's out of
these only A10 have DM_SCSI enabled. So enabling DM_MMC on A20, R40
would eventually end-up with scsi disk read failures like [1]

So, enable DM_MMC in all places of respective SoC's instead of enabling
them globally to Allwinner platform.

Now, DM_MMC is enabled in Allwinner SoC's except A20 and R40.

[1] https://lists.denx.de/pipermail/u-boot/2019-April/364057.html

Reported-by: Pablo Sebastián Greco <pgreco@centosproject.org>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>