mmc: S5P: Support DMA restarts at buffer boundaries

mmc: S5P: Support DMA restarts at buffer boundaries

Currently if a DMA buffer straddles a buffer alignment boundary
(512KiB) then the DMA engine will pause and generate a DMA
interrupt.  Since the DMA interrupt is not enabled it will hang
the MMC driver.

This patch adds support for restarting the DMA transfer.  The
SYSTEM_ADDRESS register contains the next address that would have
been read/written when a boundary is hit.  So we can read that
and write it back.  The write triggers the resumption of the
transfer.

Signed-off-by: Anton Staaf <[email protected]>
Signed-off-by: Minkyu Kang <[email protected]>
Tested-by : Jaehoon Chung <[email protected]>
Cc: Albert ARIBAUD <[email protected]>