net: dsa: qca8k: use dsa_for_each macro instead of for loop

Convert for loop to dsa_for_each macro to save some redundant write on
unconnected/unused port and tidy things up.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://lore.kernel.org/r/20230730074113.21889-5-ansuelsmth@gmail.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>