net: dsa: qca8k: Enable RXMAC when bringing up a port

When a port is brought up/down do not enable/disable only the TXMAC
but the RXMAC as well. This is essential for the CPU port to work.

Fixes: 6b93fb46

 ("net-next: dsa: add new driver for qca8xxx family")
Signed-off-by: Michal Vokáč <michal.vokac@ysoft.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>