clk: qcom: gpucc-sc8280xp: Add external supply for GX gdsc

On SA8295P and SA8540P the GFX rail is powered by a dedicated external
regulator, instead of the rpmh-controlled "gfx.lvl".

Define the "vdd-gfx" as the supply regulator for the GDSC, to cause the
gdsc logic to look for, and control, this external power supply.
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc.com>
Link: https://lore.kernel.org/r/20240125-sa8295p-gpu-v4-3-7011c2a63037@quicinc.comSigned-off-by: Bjorn Andersson <andersson@kernel.org>

drivers/clk/qcom/gpucc-sc8280xp.c

@@ -399,6 +399,7 @@ static struct gdsc gx_gdsc = {
 	},
 	.pwrsts = PWRSTS_OFF_ON,
 	.flags = CLAMP_IO | RETAIN_FF_ENABLE,
+	.supply = "vdd-gfx",
 };
 
 static struct gdsc *gpu_cc_sc8280xp_gdscs[] = {