dt-bindings: qpnp-lcdb-regulator: Add support for some LCDB DT properties

Add support for the following LCDB devicee tree properties:
"qcom,high-p2-blank-time-ns" to control the higher clamp threshold for
p2 minimum on time.
"qcom,low-p2-blank-time-ns" to control the lower clamp threshold for
p2 minimum on time.
"qcom,mpc-current-thr-ma" to control the mpc threshold for inductor
current after start up is done.

Change-Id: Ibc095328035bb52899846587e3db711a5c8296f2