[AArch64] Add REQUIRES: aarch64-registered-target to mixed-neon-types.c

Update the new test added in llvm#126945

Author: davemgreen

clang/test/CodeGen/AArch64/mixed-neon-types.c

@@ -1,6 +1,7 @@
 // NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --version 5
 // RUN: %clang_cc1  -triple aarch64-linux-gnu -target-feature +neon -x c %s -emit-llvm -o - | FileCheck %s --check-prefix=CHECK-C
 // RUN: %clang_cc1  -triple aarch64-linux-gnu -target-feature +neon -x c++ %s -emit-llvm -o - | FileCheck %s --check-prefix=CHECK-CPP
+// REQUIRES: aarch64-registered-target
 
 typedef __Uint32x4_t X;