[SPARC64]: Fix BACKOFF_SPIN on non-SMP.

It can't be just empty, it has to at least branch
back to 'label'.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/asm-sparc64/backoff.h

@@ -21,7 +21,9 @@
 #else
 
 #define BACKOFF_SETUP(reg)
-#define BACKOFF_SPIN(reg, tmp, label)
+#define BACKOFF_SPIN(reg, tmp, label) \
+	ba,pt	%xcc, label; \
+	 nop;
 
 #endif