ath6kl: Minor cleanup in msg_look_ahead parameter in ath6kl_htc_rxmsg_pending_handler()

It is just a four byte information of the received message
from ath6kl_htc_rxmsg_pending_handler(). Remove unnecessary
array representaion.

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