ralink: improve r43200

r43200 tries to detect if the fixup is needed or not. control the behaviour via
OF instead and disable unused ports.

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

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@43201 3c298f89-4303-0410-b956-a3cf2f4a3e73