bnx2x: Fix CL73 autoneg issues

- Advertise 1G KX4 in CL73 when 1G speed capability is enabled
- Add flow-control negotiation over CL73
- External loopback test on Serdes should be done in FORCE mode, since in
CL73 it is unable to link up with the same core using AUTONEG
- Fix bnx2x_set_led function to support CL73 link leds

Signed-off-by: Yaniv Rosner <yanivr@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>