mwifiex: fix Tx timeout issue during suspend test

Call netif_carrier_off/on while stoping/starting netdev queues.
This fixes netdev watchdog warning and ->ndo_tx_timeout() invocation
during suspend resume stress test.

Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Fixes: 54f00849

 ('mwifiex: Empty Tx queue during suspend')
Tested-by: Wei-Ning Huang <wnhuang@chromium.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>