ath6kl: Fix random rx data corruption

The skb->tail pointer of rx buffers is not adjusted
after skb->data pointer is aligned to 4-byte, this
causes random rx data corruption.

Signed-off-by: Jin Navy <nhjin@qca.qualcomm.com>
Signed-off-by: Vasanthakumar Thiagarajan <vthiagar@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>