net: dsa: lantiq_gswip: merge gswip_vlan_add_unaware() and gswip_vlan_add_aware()

net: dsa: lantiq_gswip: merge gswip_vlan_add_unaware() and gswip_vlan_add_aware()

The two functions largely duplicate functionality. The differences
consist in:

- the "fid" passed to gswip_vlan_active_create(). The unaware variant
  always passes -1, the aware variant passes fid = priv->vlans[i].fid,
  where i is an index into priv->vlans[] for which priv->vlans[i].bridge
  is equal to the given bridge.

- the "vid" is not passed to gswip_vlan_add_unaware(). It is implicitly
  GSWIP_VLAN_UNAWARE_PVID (zero).

- The "untagged" is not passed to gswip_vlan_add_unaware(). It is
  implicitly true. Also, the CPU port must not be a tag member of the
  PVID used for VLAN-unaware bridging.

- The "pvid" is not passed to gswip_vlan_add_unaware(). It is implicitly
  true.

- The GSWIP_PCE_DEFPVID(port) register is written by the aware variant
  with an "idx", but with a hardcoded 0 by the unaware variant.

Merge the two functions into a single unified function without any
functional changes.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Link: https://patch.msgid.link/2be190701d4c17038ce4b8047f9fb0bdf8abdf6e.1760566491.git.daniel@makrotopia.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>