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>