mwifiex: access rx_reorder_tbl_ptr only while holding lock

This patch fixes a bug in which rx_reorder_tbl_ptr is accessed
without holding spinlock at few places.

Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>