ARM: dts: msm: Update regulator supply name for msm8974

There should not be underscore in the property name.
Remove the underdcore in the regulator supply name defined
in msm-thermal device tree.

Change-Id: Id4949d8ca9d9d14ad2a8862d94571d070326d45e
Signed-off-by: Jennifer Liu <chihning@codeaurora.org>