mwifiex: Log an error on command failure during key-material upload

Sometimes the KEY_MATERIAL command can fail with the 88W8897 firmware
(when this happens exactly seems pretty random). This appears to prevent
the access point from starting, so it seems like a good idea to log an
error in that case.

Signed-off-by: Jonas Dreßler <verdre@v0yd.nl>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20211016153244.24353-3-verdre@v0yd.nl