[SCSI] ufshcd-pltfrm: remove unnecessary dma_set_coherent_mask() call

Changing the device coherent dma mask to the value that currently set
has no effect.

Signed-off-by: Akinobu Mita <mita@fixstars.com>
Signed-off-by: Santosh Y <santoshsy@gmail.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>