staging: mt7621-mmc: Remove flags from msdc_dma

The flags of msdc_dma are set to a constant value, so block and dword
padding are disabled and checksum is enabled. By removing the field
the code is easier to read and the difference to the mtk-sd driver is
smaller.

Signed-off-by: Christian Lütke-Stetzkamp <christian@lkamp.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>