mwifiex: fix incomplete scan in case of IE parsing error

A scan request is split into multiple scan commands queued in
scan_pending_q. Each scan command will be sent to firmware and
its response is handlded one after another.

If any error is detected while parsing IE in command response
buffer the remaining data will be ignored and error is returned.

We should check if there is any more scan commands pending in
the queue before returning error. This ensures that we will call
cfg80211_scan_done if this is the last scan command, or send
next scan command in scan_pending_q to firmware.

Cc: "3.6+" <stable@vger.kernel.org>
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>