net: phy: bcm7xxx: properly clear AFE_RX_LP_COUNTER

The AFE_RX_LP_COUNTER kept the last 3 bits set, which would not properly
clear the EEE LPI mode errors bits. Make sure that those bits are set to
0 to ensure the PHY timing is always good even during EEE wake-up.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>