MLK-16354-1 mmc: sdhci: add usdhc support for IOMMU

MLK-16354-1 mmc: sdhci: add usdhc support for IOMMU

The default max segment size of IOMMU is 64KB, which exceed the ADMA
limitation. ADMA only support max to 65535, 64KB - 1Byte. IOMMU will
optimize the segments it received, merge the little segment into one
big segment. If we use the default IOMMU config, then ADMA will get
some segments which it's size is 64KB. Then ADMA error will shows up.

Currently, when use standard tuning, driver default disable DMA. But
on i.MX usdhc, this is not enough. Need also clear DMA_SEL. If not,
once the DMA_SEL select AMDA2, even dma already disabled, when send
tuning command, usdhc will still prefetch the ADMA script from wrong
DMA address, then we will see IOMMU report some error which show
lack of TLB mapping.

This patch fix these two issue, make sure usdhc can work well by
operate data through IOMMU.

Signed-off-by: Haibo Chen <haibo.chen@nxp.com>