[PATCH] rt2x00: Fix antenna selection.

In the config() handler, make sure that we do configure an antenna if the
current active antenna is uninitialized. Furthermore, don't overwrite the
active antenna with bogus values if we didn't touch the antenna setup.

Signed-off-by: Mattias Nissler <mattias.nissler@gmx.de>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>