make aarch64 atomic_arch.h report that it defines pointer-sized ll/sc

at present this is done only for consistency, since this file defines
its own a_cas_p rather than using the new generic one from atomic.h
added in commit 225f6a6b5b7173b6655e4f5d49b5b9fea70bf3bb. these
definitions may however be useful if we ever need to add other
pointer-sized atomic operations.

arch/aarch64/atomic_arch.h

@@ -34,6 +34,7 @@ static inline int a_cas(volatile int *p, int t, int s)
 	return old;
 }
 
+#define a_ll_p a_ll_p
 static inline void *a_ll_p(volatile void *p)
 {
 	void *v;
@@ -41,6 +42,7 @@ static inline void *a_ll_p(volatile void *p)
 	return v;
 }
 
+#define a_sc_p a_sc_p
 static inline int a_sc_p(volatile int *p, void *v)
 {
 	int r;