ALSA: seq: Check validity before creating a port object

The client type and the port info validity check should be done before
actually creating a port, instead of unnecessary create-and-scratch.

Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20230523075358.9672-23-tiwai@suse.de


Signed-off-by: Takashi Iwai <tiwai@suse.de>