rt2x00: Fix rt2x00lib_reset_link_tuner()

rt2x00lib_reset_link_tuner() can be called from within
the link tuner itself. This means that it should
_not_ call rt2x00lib_stop_link_tuner() since that will
cause the thread to hang.

Reorder the things that should be done during a
link tuner reset and during a link tuner start.

Also make antenna tuning the last step of the link
tuner since it could possibly reset some statistical
information which we need for average calculation.

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>