bnx2x: Fix 578xx-KR 1G link

Fix a problem where 578xx-KR is unable to get link when connected to 1G link
partner. Two fixes were required:
One was to force CL37 sync_status low to prevent Warpcore from getting stuck in
CL73 parallel detect loop while link partner is sending.
Second fix was to enable auto-detect mode, thus allowing the Warpcore to select
the higher speed protocol between 10G-KR (over CL73), or go down to 1G over CL73
when there's indication for it.

Signed-off-by: Yaniv Rosner <yanivr@broadcom.com>
Signed-off-by: Ariel Elior <ariele@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>