mwifiex: replace rx_pkt_lock by rx_reorder_tbl_lock

At present driver spinlock protects iteration of list
rx_reorder_tbl_ptr with rx_reorder_tbl_lock. To protect the
individual items in this list, it uses rx_pkt_lock. But, we can
use a single rx_reorder_tbl_lock for both purposes. This patch
replaces rx_pkt_lock by rx_reorder_tbl_lock.

Signed-off-by: Ganapathi Bhat <gbhat@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>