wl1271: Fix IRQ enable handling on FW init failure

Disable IRQ's after FW initialization failure - originally this was not
done in all cases, and it resulted in a kernel warning if firmware
initialization was tried again without reboot.

Signed-off-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Reviewed-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>