dwmmc: Fix MMCCAM block size support

When using SDIO the block size if per function and most of the time
not equal to MMC_SECTOR_SIZE, fix sdio on dwmmc by setting the correct
block size in the mmc registers.

MFC after: 1 month
Sponsored by: Diablotin Systems

(cherry picked from commit 990a1dbf6fe1a9f4dc491d3e4e276034919b94f3)