ALSA: hda - Fix missing bass speaker on ASUS N550

The laptop has a built-in speaker on NID 0x1a.  It's an LFE only on
the right channel, so we need to provide an explicit chmap, too.

There might be other surround speakers, but they can fixed in addition
at later point, so let's fix the easier bass speaker at first.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=65091


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