net: dsa: qca8k: remove redundant check in parse_port_config

The very next check for port 0 and 6 already makes sure we don't go out
of bounds with the ports_config delay table.
Remove the redundant check.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>