mwifiex: process TX even when scan is ongoing

With channel scan gap, FW comes back to connected channel after each
single channel scan. So we can safely transfer data to FW during scan.
FW would send this data once on connected channel.

Signed-off-by: Avinash Patil <patila@marvell.com>
Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Cathy Luo <cluo@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>