fuse: Always flush the page cache before FOPEN_DIRECT_IO write

This was done as condition on direct_io_allow_mmap, but I believe
this is not right, as a file might be open two times - once with
write-back enabled another time with FOPEN_DIRECT_IO.

Signed-off-by: Bernd Schubert <[e-mail]>
Signed-off-by: Miklos Szeredi <[e-mail]>

fs/fuse/file.c

···
 	if (!ia)
 		return -ENOMEM;
 
-	if (fopen_direct_io && fc->direct_io_allow_mmap) {
+	if (fopen_direct_io) {
 		res = filemap_write_and_wait_range(mapping, pos, pos + count - 1);
 		if (res) {
 			fuse_io_free(ia);