ARM: dts: qcom: Change the graphics clock MX voltage corner

The graphics RCG needs to vote for turbo voltage corner
while running at its highest frequency.

Change-Id: I7d7a9f8c73f55fb30e77a0fce2433e9ef5754ff6
Signed-off-by: Deepak Katragadda <dkatraga@codeaurora.org>