ARM: Change dmb domain for bionic_atomic_barrier()

This patch changes the domain that the memory barrier operates on. Assumes
that the scope of bionic_atomic_barrier() does not include device memory,
memory shared with the GPU or any other memory external to the processor
cluster.

Change-Id: I291e741c98a64c86f3a3cf99811bbf1e714ac9aa
Signed-off-by: Serban Constantinescu <serban.constantinescu@arm.com>

libc/private/bionic_atomic_gcc_builtin.h

@@ -25,7 +25,7 @@
  * the architecture-specific assembler versions.
  */
 
-__ATOMIC_INLINE__ void __bionic_memory_barrier(void) {
+__ATOMIC_INLINE__ void __bionic_memory_barrier() {
   __sync_synchronize();
 }