ath10k: remove redundant error check

The check on ret for an error is redundant because it is already been
checked for non-zero earlier on and ret is never non-zero at this point.
Fix this by removing the redundant check and error message.

Detected by CoverityScan, CID#1357170 ("Logically Dead Code")

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>