mmc: uniphier-sd: add UniPhier SD/eMMC controller driver

Here is another TMIO MMC variant found in Socionext UniPhier SoCs.

As commit b6147490e6aa ("mmc: tmio: split core functionality, DMA and
MFD glue") said, these MMC controllers use the IP from Panasonic.

However, the MMC controller in the TMIO (Toshiba Mobile IO) MFD chip
was the first upstreamed user of this IP.  The common driver code
for this IP is now called 'tmio-mmc-core' in Linux although it is a
historical misnomer.

Anyway, this driver select's MMC_TMIO_CORE to borrow the common code
from tmio-mmc-core.c

Older UniPhier SoCs (LD4, Pro4, sLD8) support the external DMA engine
like renesas_sdhi_sys_dmac.c.  The difference is UniPhier SoCs use a
single DMA channel whereas Renesas chips request separate channels for
RX and TX.

Newer UniPhier SoCs (Pro5 and later) support the internal DMA engine
like renesas_sdhi_internal_dmac.c  The register map is almost the same,
so I guess Renesas and Socionext use the same internal DMA hardware.
The main difference is, the register offsets are doubled for Renesas.

                        Renesas      Socionext
                        SDHI         UniPhier
  DM_CM_DTRAN_MODE      0x820        0x410
  DM_CM_DTRAN_CTRL      0x828        0x414
  DM_CM_RST             0x830        0x418
  DM_CM_INFO1           0x840        0x420
  DM_CM_INFO1_MASK      0x848        0x424
  DM_CM_INFO2           0x850        0x428
  DM_CM_INFO2_MASK      0x858        0x42c
  DM_DTRAN_ADDR         0x880        0x440
  DM_DTRAN_ADDREX        ---         0x444

This comes from the difference of host->bus_shift; 2 for Renesas SoCs,
and 1 for UniPhier SoCs.  Also, the datasheet for UniPhier SoCs defines
DM_DTRAN_ADDR and DM_DTRAN_ADDREX as two separate registers.

It could be possible to factor out the DMA common code by introducing
some hooks to cope with platform quirks, but this patch does not touch
that for now.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

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