tg3: Relocate APE mutex regs for 5717+

The 5717 and later devices relocate the APE mutex registers.  This patch
organizes the code so that the driver can use the mutex registers in the
old and new locations.

Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>