dma/mic_x100_dma: IS_ERR() vs PTR_ERR() typo

This is harmless because the caller only cares about zero vs non-zero
but we should be returning PTR_ERR() here.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>