bnx2x: KR2 disablement fix

Relocate bnx2x_disable_kr2 function, and use it to disable KR2 in case it is not
configured in order to clear it's configuration, otherwise the link may come up
at 20G instead of the requested 10G-KR. In addition, restart AN after
disabling KR2 as part of the KR2 work-around.

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>