tg3: Migrate tg3_flags to phy_flags

This patch moves most of the phy related flag definitions over to the
phyflags member and changes the code accordingly.

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