ALSA: hda - Fix default multichannel HDMI mapping regression

Commit d45e6889 ("ALSA: hda - Provide
the proper channel mapping for generic HDMI driver") added support for
custom channel maps in the HDA HDMI driver. Due to a mistake in an
'if' condition the custom map is always used even when no such map has
been set. This causes incorrect channel mapping for multichannel audio
by default.

Pass per_pin->chmap_set to hdmi_setup_channel_mapping() as a parameter
so that it can use it for detecting if a custom map has been set instead
of checking if map is NULL (which is never the case).

Reported-by: Staffan Lindberg <pike@xbmc.org>
Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
Cc: stable@vger.kernel.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>