net: stmmac: dwmac1000: fix out-of-bounds mac address reg setting

net: stmmac: dwmac1000: fix out-of-bounds mac address reg setting

Commit d27d3176050d ("net: stmmac: dwmac1000: Clear unused address
entries") cleared the unused mac address entries, but introduced an
out-of bounds mac address register programming bug -- After setting
the secondary unicast mac addresses, the "reg" value has reached
netdev_uc_count() + 1, thus we should only clear address entries
if (addr < perfect_addr_number)

Fixes: d27d3176050d ("net: stmmac: dwmac1000: Clear unused address entries")
Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Signed-off-by: David S. Miller <davem@davemloft.net>