Since AR9280 v1.0 was never sold (and the initvals removed), v1.0 specific
revision checks can be removed and the 'v2.0 or later' check can be
simplified to a check for AR9280 or later.
Signed-off-by: NFelix Fietkau <nbd@openwrt.org>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>