dmaengine: fix spelling mistake "exceds" -> "exceeds"

There are a couple of spelling mistakes in dev_err error messages.
Fix them.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20200316091653.110984-1-colin.king@canonical.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>