alloc_file(): switch to passing O_... flags instead of FMODE_... mode

... so that it could set both ->f_flags and ->f_mode, without callers
having to set ->f_flags manually.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/mm/memfd.c b/mm/memfd.c
index 2706951..2bb5e25 100644
--- a/mm/memfd.c
+++ b/mm/memfd.c
@@ -326,7 +326,7 @@ SYSCALL_DEFINE2(memfd_create,
 		goto err_fd;
 	}
 	file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
-	file->f_flags |= O_RDWR | O_LARGEFILE;
+	file->f_flags |= O_LARGEFILE;
 
 	if (flags & MFD_ALLOW_SEALING) {
 		file_seals = memfd_file_seals_ptr(file);