kfifo: disable __kfifo_must_check_helper()

This helper is wrong: it coerces signed values into unsigned ones, so code
such as

	if (kfifo_alloc(...) < 0) {
		error
	}

will fail to detect the error.

So let's disable __kfifo_must_check_helper() for 2.6.36.

Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Stefani Seibold <stefani@seibold.net>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/kfifo.h

@@ -171,11 +171,8 @@ struct kfifo_rec_ptr_2 __STRUCT_KFIFO_PTR(unsigned char, 2, void);
 	}
 
 
-static inline unsigned int __must_check
-__kfifo_must_check_helper(unsigned int val)
-{
-	return val;
-}
+/* __kfifo_must_check_helper() is temporarily disabled because it was faulty */
+#define __kfifo_must_check_helper(x) (x)
 
 /**
  * kfifo_initialized - Check if the fifo is initialized