bnx2x: Fix warning message during 57712/8727 initialization

bnx2x: Fix warning message during 57712/8727 initialization

Clear warning message "MDC/MDIO access timeout" during first driver load by setting MDIO clock.
This warning has no significant meaning, since it occurs prior to the first PHY initialization.

(cherry picked from commit 7d09926d1decb658d4e24f70216b6b0b74168026)
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>
Signed-off-by: Joe Jin <joe.jin@oracle.com>