mwifiex: increase dwell time for active scan

It's been observed that sometimes AP's probe response is
received after scan duration gets completed for the channel.
This happens especially when wildcard scan is performed
along with specific SSID scan.
We will increase the time from 30 msecs to 40 msecs.

Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>