rt2x00: Implement support for rt2800usb

Add support for the rt2800usb chipset.

Current problems:
 * Cannot scan 11n AP's
 * No TX during first minute after association
 * Broken Hardware encryption

Includes various patches from Mattias, Felix, Xose and Axel.

Signed-off-by: Mattias Nissler <mattias.nissler@gmx.de>
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: Xose Vazquez Perez <xose.vazquez@gmail.com>
Signed-off-by: Axel Kollhofer <rain_maker@root-forum.org>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/rt2x00/rt2x00.h b/drivers/net/wireless/rt2x00/rt2x00.h
index ebe5f27..8d933ee 100644
--- a/drivers/net/wireless/rt2x00/rt2x00.h
+++ b/drivers/net/wireless/rt2x00/rt2x00.h
@@ -147,6 +147,7 @@
 #define RT2561		0x0302
 #define RT2661		0x0401
 #define RT2571		0x1300
+#define RT2870		0x1600
 
 	u16 rf;
 	u32 rev;