[WEXT]: Cleanup early ioctl call path.

This patch makes the code in wireless_process_ioctl somewhat more
readable.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>