rt2x00: Simplify suspend/resume handling

With mac80211 handling all open interfaces during
suspend and resume we can simplify suspend/resume
within rt2x00lib.

The only thing rt2x00 needs to do is free up memory
during suspend and bring back the minimal required
components during resume.

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