b43: Add support for 4318E

Added support for the Broadcom 4318E chipset on PCMCIA/CF cards. The
4318E can do 802.11A/B/G, only B and G mode are supported in b43.

Signed-off-by: Clyde McPherson <ccmcphe@verizon.net>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>