rt2x00: Implement support for rt2800pci

Add support for the rt2860/rt3090 chipsets from Ralink.

Includes various patches from a lot of people who helped
getting this driver into the current shape.

Signed-off-by: Alban Browaeys <prahal@yahoo.com>
Signed-off-by: Benoit PAPILLAULT <benoit.papillault@free.fr>
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: Luis Correia <luis.f.correia@gmail.com>
Signed-off-by: Mattias Nissler <mattias.nissler@gmx.de>
Signed-off-by: Mark Asselstine <asselsm@gmail.com>
Signed-off-by: Xose Vazquez Perez <xose.vazquez@gmail.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>