zsmalloc: use U suffix for negative literals being shifted

Fix warning about shifting unsigned literals being undefined behavior.

Link: http://lkml.kernel.org/r/1515642078-4259-1-git-send-email-nick.desaulniers@gmail.com
Signed-off-by: Nick Desaulniers <nick.desaulniers@gmail.com>
Suggested-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Nick Desaulniers <nick.desaulniers@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/zsmalloc.c

@@ -1047,7 +1047,7 @@ static void init_zspage(struct size_class *class, struct zspage *zspage)
 			 * Reset OBJ_TAG_BITS bit to last link to tell
 			 * whether it's allocated object or not.
 			 */
-			link->next = -1 << OBJ_TAG_BITS;
+			link->next = -1UL << OBJ_TAG_BITS;
 		}
 		kunmap_atomic(vaddr);
 		page = next_page;