This enables the headset microphone on Dell Inspiron 5548,
or at least some variants of it.

Cc: stable@vger.kernel.org
BugLink: https://bugs.launchpad.net/bugs/1452175Signed-off-by: NDavid Henningsson <david.henningsson@canonical.com>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>