dt-bindings: Add DT bindings for hbtp_input

Add DT binding for hbtp_input.
This is a snapshot of dt-bindings files as of msm-4.9
'commit 8f7046d0c282 (" Merge "msm: ep_pcie: Disable
clkreq interrupt and release wakelock in D3 cold")'.

Change-Id: I475411df7d87c150579ca10a2ba78b14a91811b0