rt2x00: rt2800 - Fix default vgc values for RT3572

Align with the values used by the RT3572 Ralink vendor driver v2.5.0.0.

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