commit 2ecb704a upstream.

Latest Thinkpad laptops use the HKEY_HID LEN0268 instead of the
LEN0068, as a result neither audio mute led nor mic mute led can work
any more.

After adding the new HKEY_HID into the is_thinkpad(), both of them
works well as before.
Signed-off-by: Hui Wang <hui.wang@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
[bwh: Backported to 3.16: use acpi_get_devices() instead of acpi_dev_found()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>