sh: add J2 atomics using the cas.l instruction

Signed-off-by: Rich Felker <dalias@libc.org>

arch/sh/include/asm/atomic.h

@@ -1,6 +1,12 @@
 #ifndef __ASM_SH_ATOMIC_H
 #define __ASM_SH_ATOMIC_H
 
+#if defined(CONFIG_CPU_J2)
+
+#include <asm-generic/atomic.h>
+
+#else
+
 /*
  * Atomic operations that C can't guarantee us.  Useful for
  * resource counting etc..
@@ -63,4 +69,6 @@ static inline int __atomic_add_unless(atomic_t *v, int a, int u)
 	return c;
 }
 
+#endif /* CONFIG_CPU_J2 */
+
 #endif /* __ASM_SH_ATOMIC_H */