Don't build bcm43xx if SSB is static and b43 PCI-SSB bridge is enabled.

This may happen e.g. when the ssb is statically enables by the b44 driver,
and the b43 pci-ssb bridge is enbled by the b43/b43legacy drivers, or the
b43/b43legacy drivers are built statically.

Signed-off-by: Alexey Zaytsev <alexey.zaytsev@gmail.com>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>