mv643xx_eth: fix unicast filter programming in promiscuous mode

The Unicast Promiscious Mode (UPM) bit in the mv643xx_eth port
configuration register doesn't do exactly what its name would suggest:
setting this bit merely enables reception of all unicast frames with a
destination address that differs from our local MAC address in bits
[47:4].  In particular, it doesn't have any effect on unicast frames
with a destination address that matches our MAC address in bits [47:4]
-- these will still be tested against the 16-entry unicast address
filter table.

Therefore, if the interface is set to promiscuous mode, just setting
the unicast promiscuous bit isn't enough -- we need to set all filter
bits in the unicast filter table to 1 as well.

Reported-by: Sachin Sanap <ssanap@marvell.com>
Signed-off-by: Prabhanjan Sarnaik <sarnaik@marvell.com>
Tested-by: Siddarth Gore <gores@marvell.com>
Tested-by: Mahavir Jain <mjain@marvell.com>
Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>
Cc: stable@kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>