[libc] Use correct mnemonic for arm64_32 architecture

arm64_32 is an ILP32 platform

Differential Revision: https://reviews.llvm.org/D124134

libc/src/string/memory_utils/elements_aarch64.h

@@ -55,7 +55,11 @@ using _64 = Chained<_32, _32>;
 struct ZVA {
   static constexpr size_t SIZE = 64;
   static void splat_set(char *dst, const unsigned char value) {
+#if __SIZEOF_POINTER__ == 4
+    asm("dc zva, %w[dst]" : : [dst] "r"(dst) : "memory");
+#else
     asm("dc zva, %[dst]" : : [dst] "r"(dst) : "memory");
+#endif
   }
 };