dt-bindings: leds: Add snapshot of vibrator LDO for lito

This is a snapshot of the vibrator LDO Documentation as of msm-4.14
'commit Ib18fb4bdb6e (Merged "leds: qpnp: add driver file for
configuring vibrator LDO")'.

Change-Id: I49df062c27bfd54b9b0658eb97526be2c2251499
Signed-off-by: Umang Agrawal <uagrawal@codeaurora.org>