mm: simplify try_to_unuse

mm: simplify try_to_unuse

Remove the unused frontswap and pages_to_unuse arguments, and mark the
function static now that the caller in frontswap is gone.

[[email protected]: fix shmem_unuse() stub, per Matthew]

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Juergen Gross <[email protected]>
Cc: Dan Streetman <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Konrad Rzeszutek Wilk <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Seth Jennings <[email protected]>
Cc: Vitaly Wool <[email protected]>
Cc: Naresh Kamboju <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>