b43: Remove EXPERIMENTAL designation from LP PHY selection

Since kernel 3.0, the problems with controlling b43 devices that have
low-power (LP) PHYs have been fixed and the EXPERIMENTAL designation
can be fixed.

This patch also fixes a typo as the device supports 802.11b communications.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Acked-by: Rafał Miłecki <zajec5@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>