[PATCH] rt2x00: Correct error in calculating rssi for link tuner

The call to rt2x00lib_precalculate_link_signal resets link.rx_success
which is needed when calculating the average rssi for the link
tuner. Change the call order so the link tuner runs first as it
doesn't need the result of the precalculate.

Signed-off-by: Adam Baker <linux@baker-net.org.uk>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>