ARM: dts: msm: update MX regulator handle for CPR

CPR votes on active set of MX regulator, update CPR's
MX regulator handle entry in device tree to reflect the same.

Change-Id: I89b958f9e7e7251ff15abed3d57ba7ecdc094e36
Signed-off-by: Ashay Jaiswal <ashayj@codeaurora.org>