wifi: iwlwifi: use normal versioning convention for iwl_tx_cmd

wifi: iwlwifi: use normal versioning convention for iwl_tx_cmd

We have iwl_tx_cmd for devices older than 22000, iwl_tx_cmd_gen2 for
22000 devices, and iwl_tx_cmd_gen3 ax210 and up.

But the convention for all other APIs is to have the latest version
without any prefix and the older ones - with a _vX prefix,
where X is the highest version that this struct support.

The  term 'gen' was introduced as the name of the (back then) new
transport, and should not be used as a device name (for that we have the
actual names: 22000, ax210, etc.)

Now as a new transport, called 'gen3', is going to be written and it can
be confused with this API.

Move iwl_tx_cmd to use the regular versioning convention.

Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250511195137.806e40c8f767.Ibc0e95e43a6fa6d47f72823bf804314d5db84618@changeid