mm: fix the try_to_unmap prototype for !CONFIG_MMU

Adjust the nommu stub of try_to_unmap to match the changed protype for the
full version.  Turn it into an inline instead of a macro to generally
improve the type checking.

Link: https://lkml.kernel.org/r/20210705053944.885828-1-hch@lst.de
Fixes: 1fb08ac6 ("mm: rmap: make try_to_unmap() void function")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/rmap.h

@@ -291,7 +291,9 @@ static inline int page_referenced(struct page *page, int is_locked,
 	return 0;
 }
 
-#define try_to_unmap(page, refs) false
+static inline void try_to_unmap(struct page *page, enum ttu_flags flags)
+{
+}
 
 static inline int page_mkclean(struct page *page)
 {