tg3: Create critical section around GPIO toggling

tg3: Create critical section around GPIO toggling

The code that performs the power source switching will need to consider
the status of the other devices before making any switches.  The status
updates and power source switching will need to be an atomic operation,
so a critical section will be needed.  This patch establishes the
critical section through a CPMU mutex.

Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 6f5c8f8317d37045ffc7ea21dab8319a53c1ae57)

Signed-off-by: Joe Jin <joe.jin@oracle.com>