bcma: add ext PA workaround for BCM4331 and BCM43431

MacBook Pro models with BCM4331 wireless have been found to have the ext
PA lines disabled after resuming from S3 without external power attach.
This causes them to be unable to transmit. Add a workaround to ensure
that the ext PA lines are enabled on BCM4331. Also extend all handling
of ext PA line muxing to BCM43431 as is done in the Broadcom SDK.

BugLink: http://bugs.launchpad.net/bugs/925577


Cc: Arend van Spriel <arend@broadcom.com>
Cc: Hauke Mehrtens <hauke@hauke-m.de>
Cc: stable@vger.kernel.org
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>