mm: convert page_remove_rmap() to use a folio internally

The API for page_remove_rmap() needs to be page-based, because we can
remove mappings of pages individually.  But inside the function, we want
to only call compound_head() once and then use the folio APIs instead of
the page APIs that each call compound_head().

Link: https://lkml.kernel.org/r/20230111142915.1001531-6-willy@infradead.org


Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>