ALSA: seq: Allow suppressing UMP conversions

A sequencer client like seq_dummy rather doesn't want to convert UMP
events but receives / sends as is.  Add a new event filter flag to
suppress the automatic UMP conversion and applies accordingly.

Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20230523075358.9672-32-tiwai@suse.de


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