mwifiex: shorten per channel scan time

Currently the scan time per channel for active scanning is set to
200ms. It takes quite a while to finsh scanning on all channels,
especially with a dual band configuration.

Change the per channel scan time settings to the following values:

passive scan: 110ms
active scan: 30ms
specific scan: 30ms

Above settings have been tested on x86 and arm platforms.

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