atomic_t: Cast to volatile when accessing atomic variables

In preparation for removing volatile from the atomic_t definition, this
patch adds a volatile cast to all the atomic read functions.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/asm-generic/atomic.h b/include/asm-generic/atomic.h
index c99c64d..c33749f 100644
--- a/include/asm-generic/atomic.h
+++ b/include/asm-generic/atomic.h
@@ -33,7 +33,7 @@
  * Atomically reads the value of @v.  Note that the guaranteed
  * useful range of an atomic_t is only 24 bits.
  */
-#define atomic_read(v)	((v)->counter)
+#define atomic_read(v)	(*(volatile int *)&(v)->counter)
 
 /**
  * atomic_set - set atomic variable