ath5k: minor rfkill cleanup

Always enable rfkill since the ifdefs in the code is not really worth
the Kconfig option.  Also fix a few code style things, and remove the
usage of the ah_gpio[] array so we can remove it later.

Signed-off-by: Bob Copeland <me@bobcopeland.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>