arm64: dts: qcom: sc8280xp: fix external display power domain

Fix the external display controller nodes which erroneously described
the controllers as belonging to CX rather than MMCX.

Fixes: 19d3bb90 ("arm64: dts: qcom: sc8280xp: Add USB-C-related DP blocks")
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230316141252.2436-1-johan+linaro@kernel.org

arch/arm64/boot/dts/qcom/sc8280xp.dtsi

@@ -3267,7 +3267,7 @@ mdss0_dp0: displayport-controller@ae90000 {
 				#sound-dai-cells = <0>;
 
 				operating-points-v2 = <&mdss0_dp0_opp_table>;
-				power-domains = <&rpmhpd SC8280XP_CX>;
+				power-domains = <&rpmhpd SC8280XP_MMCX>;
 
 				status = "disabled";
 
@@ -3345,7 +3345,7 @@ mdss0_dp1: displayport-controller@ae98000 {
 				#sound-dai-cells = <0>;
 
 				operating-points-v2 = <&mdss0_dp1_opp_table>;
-				power-domains = <&rpmhpd SC8280XP_CX>;
+				power-domains = <&rpmhpd SC8280XP_MMCX>;
 
 				status = "disabled";