ralink: add mt7621 support

there are still various missing pieces for full support.

Signed-off-by: John Crispin <blogic@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@39040 3c298f89-4303-0410-b956-a3cf2f4a3e73
iw: reduce size and make the phy dump output more readable

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@39041 3c298f89-4303-0410-b956-a3cf2f4a3e73