be2net: Fix UE detection logic for BE3

On certain platforms BE3 chips may indicate spurious UEs (unrecoverable
error). Because of the UE detection logic was disabled in the driver
for BE3 chips. Because of this, even in cases of a real UE,
a failover will not occur. This patch re-enables UE detection on BE3
and if a UE is detected, reads the POST register. If the POST register,
reports either a FAT_LOG_STATE or a ARMFW_UE, then it means that a valid
UE occurred in the chip.

Signed-off-by: Suresh Reddy <suresh.reddy@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>