arm64: dts: qcom: sm8250: Add missing CPU7 3.09GHz OPP

This resolves the following error seen on the ASUS ROG Phone 3:

cpu cpu7: Voltage update failed freq=3091200
cpu cpu7: failed to update OPP for freq=3091200

Fixes: 8e0e801 ("arm64: dts: qcom: sm8250: Add CPU opp tables")
Signed-off-by: Alexander Koskovich <akoskovich@pm.me>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20260307-sm8250-cpu7-opp-v1-1-435f5f6628a1@pm.me
Signed-off-by: Bjorn Andersson <andersson@kernel.org>

Author: AKoskovich

arch/arm64/boot/dts/qcom/sm8250.dtsi

@@ -665,6 +665,11 @@
 			opp-hz = /bits/ 64 <2841600000>;
 			opp-peak-kBps = <8368000 51609600>;
 		};
+
+		cpu7_opp21: opp-3091200000 {
+			opp-hz = /bits/ 64 <3091200000>;
+			opp-peak-kBps = <8368000 51609600>;
+		};
 	};
 
 	firmware {