dt-bindings: devfreq: Add dt-bindings for BWMON HW version 2

This patch adds the dt-bindings for the version 2 of the BIMC
BWMON HW.

Change-Id: I7b2a2f795dc9b7bc47bcfaa220e55ed21e7ec8e3
Signed-off-by: Rama Aparna Mallavarapu <aparnam@codeaurora.org>