rt2x00: Remove myself as maintainer.

Let's formalize what must have been blatantly clear from my level
of activity is the past year(s).
I simply do not have time for this anymore.

Signed-off-by: Gertjan van Wingerde <gwingerde@gmail.com>
Acked-by: Helmut Schaa <helmut.schaa@googlemail.com>
Acked-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>