net: phy: broadcom: fix PHY_BCM_OUI_4

PHY_BCM_OUI_4 is missing two significant digits that actually make it an
OUI, add those missing bits so it becomes usable again for matching.

Fixes: b560a58c ("net: phy: add Broadcom BCM7xxx internal PHY driver")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>