ath10k: cleanup amsdu processing for rx indication

Make amsdu handlers (i.e amsdu_pop and rx_h_handler) common to both
rx_ind and frag_ind htt events. It is sufficient to hold rx_ring lock
for amsdu_pop alone and no need to hold it until the packets are
delivered to mac80211. This helps to reduce rx_lock contention as well.

Signed-off-by: Rajkumar Manoharan <rmanohar@qti.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>