linux-gen: llsc: fix type casts error with CXX

Fix casts to union type erros with CXX on aarch64. When "odp_cpu.h" is
included in some head files, "odp_api_from_cpp.cpp" would include
"odp_cpu.h" as well. Build failure and error of 'unknown conversion of
types' show as going through this file with CXX.

Signed-off-by: Fan Hong <fan.hong@arm.com>

platform/linux-generic/arch/aarch64/odp_llsc.h

@@ -150,15 +150,15 @@ static inline uint32_t scd(_odp_u128_t *var, _odp_u128_t neu, int mm)
 	if (mm == __ATOMIC_RELEASE)
 		__asm__ volatile("stlxp %w0, %1, %2, [%3]"
 				 : "=&r" (ret)
-				 : "r" (((union i128)neu).i64[0]),
-				   "r" (((union i128)neu).i64[1]),
+				 : "r" (((*(union i128 *)&neu)).i64[0]),
+				   "r" (((*(union i128 *)&neu)).i64[1]),
 				   "r" (var)
 				 : "memory");
 	else if (mm == __ATOMIC_RELAXED)
 		__asm__ volatile("stxp %w0, %1, %2, [%3]"
 				 : "=&r" (ret)
-				 : "r" (((union i128)neu).i64[0]),
-				   "r" (((union i128)neu).i64[1]),
+				 : "r" (((*(union i128 *)&neu)).i64[0]),
+				   "r" (((*(union i128 *)&neu)).i64[1]),
 				   "r" (var)
 				 : );
 	else