Input: add support for pm8xxx based vibrator driver

Add support for pm8xx based vibrator to facilitate haptics.
This module uses the ff-memless framework.

Signed-off-by: Amy Maloche <amaloche@codeaurora.org>
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>
Reviewed-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>