m68k: Enable atomic64_t

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
diff --git a/arch/m68k/include/asm/atomic.h b/arch/m68k/include/asm/atomic.h
index 8d29145..eab36dc 100644
--- a/arch/m68k/include/asm/atomic.h
+++ b/arch/m68k/include/asm/atomic.h
@@ -3,3 +3,5 @@
 #else
 #include "atomic_mm.h"
 #endif
+
+#include <asm-generic/atomic64.h>