hp_accel: Add support for HP ZBook 15

HP ZBook 15 laptop needs a non-standard mapping (x_inverted).

BugLink: http://bugzilla.opensuse.org/show_bug.cgi?id=905329


Signed-off-by: Dominique Leuenberger <dimstar@opensuse.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>