bnxt_en: avoid link reset if speed is not changed

PORT_PHY_CONFIG is always sent with REQ_FLAGS_RESET_PHY set. This flag
must be set in order for the firmware to institute the requested PHY
change immediately, but it results in a link flap. This is unnecessary
and results in an improved user experience if the PHY reconfiguration
is avoided when the user requested speed does not constitute a change.

Signed-off-by: Edwin Peer <edwin.peer@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>