target/ppc: Fix timer register accessors when !KVM

When the Timer Control and Timer Status registers are modified, avoid
calling the KVM backend when not available

Signed-off-by: Cédric Le Goater <clg@kaod.org>

target/ppc/kvm.c

@@ -1728,6 +1728,10 @@ int kvmppc_or_tsr_bits(PowerPCCPU *cpu, uint32_t tsr_bits)
         .addr = (uintptr_t) &bits,
     };
 
+    if (!kvm_enabled()) {
+        return 0;
+    }
+
     return kvm_vcpu_ioctl(cs, KVM_SET_ONE_REG, &reg);
 }
 
@@ -1741,6 +1745,10 @@ int kvmppc_clear_tsr_bits(PowerPCCPU *cpu, uint32_t tsr_bits)
         .addr = (uintptr_t) &bits,
     };
 
+    if (!kvm_enabled()) {
+        return 0;
+    }
+
     return kvm_vcpu_ioctl(cs, KVM_SET_ONE_REG, &reg);
 }
 
@@ -1755,6 +1763,10 @@ int kvmppc_set_tcr(PowerPCCPU *cpu)
         .addr = (uintptr_t) &tcr,
     };
 
+    if (!kvm_enabled()) {
+        return 0;
+    }
+
     return kvm_vcpu_ioctl(cs, KVM_SET_ONE_REG, &reg);
 }