dmaengine: ioatdma: loop for number elements in array chanerr_str

Just iterate over the number of elements in array chanerr_str rather
than for all 32 bits.  This removes the need for a NULL chanerr_str[i]
check which could possibly overrun if the upper bits (28..31) of
chanerr are set and 27th bit in chanerr is zero. This simplifies the
code by removing an if statement and a break.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>