mwifiex: wowlan: do not disconnect on suspend

For users who do not need wowlan, load mwifiex.ko with
disconnect_on_suspend = 1; or iw phy0 wowlan disable.

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