We need to disable ext. PA lines for reading SPROM. It's disabled by
default, but this patch allows using bcma after loading wl, which leaves
workaround enabled.

Cc: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>