ipq40xx: net/ipqess: fix outbound port tag computation

ipq40xx: net/ipqess: fix outbound port tag computation

Since the introduction of out-of-band tagging, writing the outbound tag
had been completely broken: First, in place of a port mask containing
the port number, just the port number itself was set in the register
value. Just after that, the full port mask 0x3e (all 5 external ports)
was set unconditionally.

This remained unnoticed because the switch would then use the FDB to
decide where to send unicast packets; broadcast and multicast packets
were however sent to every port.

Fix the port tag computation and only use the full port mask as a
fallback for non-DSA mode, as it was done in the older driver patches
used on Linux 5.15.

Fixes: cd9c7211241e ("ipq40xx: 6.1: use latest DSA and ethernet patches")
Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>
Signed-off-by: Robert Marko <robimarko@gmail.com>