b43: Make LP-PHY testable

-Enable rate memory init for LP-PHY (same as G and N-PHY).
-Mark rev.2 LP-PHYs with the B2063 radio as supported.
-Allow using the 5GHz band on LP-PHYs.

Signed-off-by: Gábor Stefanik <netrolller.3d@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>