btrfs: fix the ASSERT() inside GET_SUBPAGE_BITMAP()

After enabling large data folios for tests, I hit the ASSERT() inside
GET_SUBPAGE_BITMAP() where blocks_per_folio matches BITS_PER_LONG.

The ASSERT() itself is only based on the original subpage fs block size,
where we have at most 16 blocks per page, thus
"ASSERT(blocks_per_folio < BITS_PER_LONG)".

However the experimental large data folio support will set the max folio
order according to the BITS_PER_LONG, so we can have a case where a large
folio contains exactly BITS_PER_LONG blocks.

So the ASSERT() is too strict, change it to
"ASSERT(blocks_per_folio <= BITS_PER_LONG)" to avoid the false alert.

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/subpage.c

@@ -666,7 +666,7 @@ IMPLEMENT_BTRFS_PAGE_OPS(checked, folio_set_checked, folio_clear_checked,
 				btrfs_blocks_per_folio(fs_info, folio);	\
 	const struct btrfs_subpage *subpage = folio_get_private(folio);	\
 									\
-	ASSERT(blocks_per_folio < BITS_PER_LONG);			\
+	ASSERT(blocks_per_folio <= BITS_PER_LONG);			\
 	*dst = bitmap_read(subpage->bitmaps,				\
 			   blocks_per_folio * btrfs_bitmap_nr_##name,	\
 			   blocks_per_folio);				\