mwifiex: restart rxreorder timer correctly

During 11n RX reordering, if there is a hole in RX table,
driver will not send packets to kernel until the rxreorder
timer expires or the table is full.
However, currently driver always restarts rxreorder timer when
receiving a packet, which causes the timer hardly to expire.
So while connected with to 11n AP in a busy environment,
ping packets may get blocked for about 30 seconds.

This patch fixes this timer restarting by ensuring rxreorder timer
would only be restarted either timer is not set or start_win
has changed.

Signed-off-by: Chin-Ran Lo <crlo@marvell.com>
Signed-off-by: Plus Chen <pchen@marvell.com>
Signed-off-by: Marc Yang <yangyang@marvell.com>
Signed-off-by: Cathy Luo <cluo@marvell.com>
Signed-off-by: Avinash Patil <patila@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>