KVM: x86: Code style cleanup in kvm_arch_dev_ioctl()

In kvm_arch_dev_ioctl(), the brackets of case KVM_X86_GET_MCE_CAP_SUPPORTED
accidently encapsulates case KVM_GET_MSR_FEATURE_INDEX_LIST and case
KVM_GET_MSRS. It doesn't affect functionality but it's misleading.

Remove unnecessary brackets and opportunistically add a "break" in the
default path.

Suggested-by: Sean Christopherson <[e-mail]>
Signed-off-by: Xiaoyao Li <[e-mail]>
Reviewed-by: Vitaly Kuznetsov <[e-mail]>
Signed-off-by: Paolo Bonzini <[e-mail]>

arch/x86/kvm/x86.c

···
 		r = 0;
 		break;
 	}
-	case KVM_X86_GET_MCE_CAP_SUPPORTED: {
+	case KVM_X86_GET_MCE_CAP_SUPPORTED:
 		r = -EFAULT;
 		if (copy_to_user(argp, &kvm_mce_cap_supported,
 				 sizeof(kvm_mce_cap_supported)))
···
 	case KVM_GET_MSRS:
 		r = msr_io(NULL, argp, do_get_msr_feature, 1);
 		break;
-	}
 	default:
 		r = -EINVAL;
+		break;
 	}
 out:
 	return r;