wl1251: fix trigger scan timeout usage

Use appropriate command (CMD_TRIGGER_SCAN_TO) instead of scan command
(CMD_SCAN) to configure trigger scan timeout.

This was broken in commit 3a98c30f.

This fix address the bug reported here:

https://bugzilla.kernel.org/show_bug.cgi?id=16554



Cc: stable@kernel.org
Signed-off-by: Yuri Ershov <ext-yuri.ershov@nokia.com>
Signed-off-by: Yuri Kululin <ext-yuri.kululin@nokia.com>
Acked-by: Kalle Valo <kvalo@adurom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>