rt2800: add support for radio chip RF3070

Add support for new RF chip ID: 3070. It seems to be the same as 5370,
maybe vendor just put wrong value on the eeprom, but add this id anyway
since devices with it showed on the marked.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>