bcachefs: Do not check folio_has_private()

folio_has_private() is an attractive nuisance; filesystem authors
generally don't realise that it actually checks two flags (one of which
is never set by bcachefs).  There's no need to check the private flag at
all; for folios owned by bcachefs, we know that folio->private is NULL
when the private flag is clear and non-NULL when the private flag is set.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/fs-io-pagecache.h

@@ -99,9 +99,7 @@ static inline void bch2_folio_release(struct folio *folio)
 
 static inline struct bch_folio *__bch2_folio(struct folio *folio)
 {
-	return folio_has_private(folio)
-		? (struct bch_folio *) folio_get_private(folio)
-		: NULL;
+	return folio_get_private(folio);
 }
 
 static inline struct bch_folio *bch2_folio(struct folio *folio)