[TG3]: add basic bcm5752 support

Add ASIC_REV_5752 definition.

Track-down all references to ASIC_REV_5750 and mirror them with
references to the newly defined ASIC_REV_5752.

Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>