net: phy: bcm7xxx: remove 28nm wildcard entry

A wildcard entry with the 32-bits OUI 0x600d8400 was added as part of
the BCM7xxx internal PHY driver, but that entry might match other PHYs
that are not covered by this driver, so let's just remove it.

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@greenl8ke.davemloft.net>