NFS: Simplify internal check for whether file is open for write

{

	struct inode *inode = &nfsi->vfs_inode;

	assert_spin_locked(&inode->i_lock);

	if (!S_ISREG(inode->i_mode))

		return false;

	if (list_empty(&nfsi->open_files))

		return false;

	/* Note: This relies on nfsi->open_files being ordered with writers

	 *       being placed at the head of the list.

	 *       See nfs_inode_attach_open_context()

	 */

	return (list_first_entry(&nfsi->open_files,

			struct nfs_open_context,

			list)->mode & FMODE_WRITE) == FMODE_WRITE;

	return inode_is_open_for_write(inode);

}

static bool nfs_file_has_buffered_writers(struct nfs_inode *nfsi)