ARM: dts: msm: Add regulator cooling device for sdm670

Add regulator cooling device for CX and MX regulator for sdm670.
The cooling device will be used to place voltage floor restriction.

Change-Id: Ieb291d131476f800ed86fbe7c5bec7d8eeb67ec5
Signed-off-by: Manaf Meethalavalappu Pallikunhi <manafm@codeaurora.org>