target-arm: kvm64: set guest PMUv3 feature bit if supported

Check if kvm supports guest PMUv3. If so, set the corresponding feature
bit for vcpu.

Backports commit 5c0a3819f009639f67ce0453dff6ec7211bfee54 from qemu

qemu/target-arm/cpu.h

@@ -581,6 +581,8 @@ typedef struct ARMCPU {
     bool powered_off;
     /* CPU has security extension */
     bool has_el3;
+    /* CPU has PMU (Performance Monitor Unit) */
+    bool has_pmu;
 
     /* CPU has memory protection unit */
     bool has_mpu;