KVM: x86: Remove break statements that will never be executed

Fix compiler warnings when compiling KVM with [-Wunreachable-code-break].
No functional change intended.

Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Like Xu <likexu@tencent.com>
Link: https://lore.kernel.org/r/20230807094243.32516-1-likexu@tencent.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

arch/x86/kvm/emulate.c

@@ -1799,13 +1799,11 @@ static int writeback(struct x86_emulate_ctxt *ctxt, struct operand *op)
 					       op->addr.mem,
 					       &op->val,
 					       op->bytes);
-		break;
 	case OP_MEM_STR:
 		return segmented_write(ctxt,
 				       op->addr.mem,
 				       op->data,
 				       op->bytes * op->count);
-		break;
 	case OP_XMM:
 		kvm_write_sse_reg(op->addr.xmm, &op->vec_val);
 		break;

arch/x86/kvm/hyperv.c

@@ -1293,7 +1293,6 @@ static bool hv_check_msr_access(struct kvm_vcpu_hv *hv_vcpu, u32 msr)
 	case HV_X64_MSR_VP_ASSIST_PAGE:
 		return hv_vcpu->cpuid_cache.features_eax &
 			HV_MSR_APIC_ACCESS_AVAILABLE;
-		break;
 	case HV_X64_MSR_TSC_FREQUENCY:
 	case HV_X64_MSR_APIC_FREQUENCY:
 		return hv_vcpu->cpuid_cache.features_eax &

arch/x86/kvm/x86.c

@@ -4646,7 +4646,6 @@ static int kvm_x86_dev_get_attr(struct kvm_device_attr *attr)
 		return 0;
 	default:
 		return -ENXIO;
-		break;
 	}
 }