DMA for MMCs can be enabled, since the previous patch fixes
the following issue in SPL:
Trying to boot from MMC1
spl: mmc init failed with error: -110
SPL: failed to boot from all boot devices
### ERROR ### Please RESET the board ###
Signed-off-by: Matwey V. Kornilov <matwey.kornilov@gmail.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>