net: dsa: qca8k: remove extra mutex_init in qca8k_setup

Mutex is already init in sw_probe. Remove the extra init in qca8k_setup.

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>