Revert "spi: Clear dma_mask for xilinx spi controller"

This reverts commit 2511d569.

Based on "https://lkml.org/lkml/2013/6/4/332

"
missing use case that's why revert this change
and look at it again if this problem comes again.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>