ARM: dts: msm: Fix get regulator MX fail in probe for SDM845 V2

regulator_get for vdd_mx is called in function GPUCC probe but the
physical power rail is connected with GFX clock node.
This change fixes that.

CRs-Fixed: 2100127
Change-Id: I4d48575a5bef36fca7ac751c153e7e5e40755dd2
Signed-off-by: Vicky Wallace <vwallace@codeaurora.org>