ALSA: seq: Add missing UMP EP cap bit at snd_seq_create_ump_endpoint()

ALSA: seq: Add missing UMP EP cap bit at snd_seq_create_ump_endpoint()

In snd_seq_create_ump_endpoint(), it was forgotten to give the UMP
Endpoint capability bit (SND_SEQ_PORT_CAP_UMP_ENDPOINT) to the port 0
("UMP 2.0").  This resulted in port 0 being a normal port for the
non-existing group.

Fixes: 6167b8ce3e80 ("seq: Add API helper functions for creating UMP Endpoint and Blocks")
Closes: https://github.com/alsa-project/alsa-lib/issues/447
Signed-off-by: Takashi Iwai <tiwai@suse.de>