arm64: dts: Add Broadcom Vulcan PMU in dts

Add "brcm,vulcan-pmu" compatible string for Broadcom Vulcan PMU.
Signed-off-by: Ashok Kumar <ashoks@broadcom.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/boot/dts/broadcom/vulcan.dtsi

@@ -86,7 +86,7 @@ timer {
 	};
 
 	pmu {
-		compatible = "arm,armv8-pmuv3";
+		compatible = "brcm,vulcan-pmu", "arm,armv8-pmuv3";
 		interrupts = <GIC_PPI 7 IRQ_TYPE_LEVEL_HIGH>; /* PMU overflow */
 	};