[TG3]: add support for bcm5752 rev a1

Replace existing ASIC_REV_5752 definition with ASIC_REV_5752_A0,
and add definition for ASIC_REV_5752_A1. Then, add ASIC_REV_5752_A1
to check for setting TG3_FLG2_5750_PLUS in tg3_get_invariants.

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