fs: Remove page_mkwrite_check_truncate()

All callers of this function have now been converted to use
folio_mkwrite_check_truncate().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Tested-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Signed-off-by: David Howells <dhowells@redhat.com>