dt-bindings: soc: qcom: Add DT bindings for QTI PBS driver

QTI PBS (Programmable Boot Sequence) driver helps triggering
certain PBS on QTI PMICs when available for APPS.

This snapshot is taken as of msm-4.14
commit 9bb584ae3a9d ("msm/sde/rotator: Add rev checks for sdmmagpie").

Change-Id: I9148ff20220b998b1634fb9c26d462b2a25d6586
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>