rcu: Remove return value from RCU_INIT_POINTER()

The return value from RCU_INIT_POINTER() is not used, and using it
would be quite ugly, for example:

	q = RCU_INIT_POINTER(global_p, p);

To prevent this sort of ugliness from appearing, this commit wraps
RCU_INIT_POINTER() in a do-while loop.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Acked-by: David Howells <dhowells@redhat.com>
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index ffe24c0..abf44d8 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -903,7 +903,9 @@
  * the reader-accessible portions of the linked structure.
  */
 #define RCU_INIT_POINTER(p, v) \
-		p = (typeof(*v) __force __rcu *)(v)
+	do { \
+		p = (typeof(*v) __force __rcu *)(v); \
+	} while (0)
 
 /**
  * RCU_POINTER_INITIALIZER() - statically initialize an RCU protected pointer