[TG3]: Correct sw autoneg flow control advertisements

This patch modifies the software autoneg code to use the administrator
specified flow control parameters.  Since the autonegotiation code uses
alternative flow control enumerations, the 1000-BaseX utility functions
are used and code was added to convert the definitions to and from the
alternate enumerations.

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>