ath10k: fix 4addr rx

The nwifi header is padded to 4 bytes. This wasn't
a problem until one tried to (at least) rx 4addr
frames.

This finally allows managed iface to be used in a
bridge.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>