b43: LP-PHY: Fix TX gain tables

The rev1 2GHz and rev2 5GHz gain tables were incorrectly documented
on the specs originally. Update these gaintables to match the cor-
rected specs.
Signed-off-by: NGábor Stefanik <netroller.3d@gmail.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>