ALSA: hda - Handle pin NID 0x1a on ALC259/269

BugLink: http://bugs.launchpad.net/bugs/582199
BugLink: http://bugs.launchpad.net/bugs/586418
BugLink: http://bugs.launchpad.net/bugs/588031

The pin NID 0x1a should be handled as well as NID 0x1b.
Also added comments.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
(cherry picked from commit b08b1637ce1c0196970348bcabf40f04b6b3d58e in
git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-2.6.git)

Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Leann Ogasawara <leann.ogasawara@canonical.com>