ALSA: seq: Fix incorrect UMP type for system messages

When converting a legacy system message to a UMP packet, it forgot to
modify the UMP type field but keeping the default type (either type 2
or 4).  Correct to the right type for system messages.

Fixes: e9e02819

 ("ALSA: seq: Automatic conversion of UMP events")
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20240529083800.5742-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>