net: dcb: fix small regression in __dcbnl_pg_setcfg()

A small regression was introduced in the reply command of
dcbnl_pg_setcfg(). User space apps may be expecting the
DCB_ATTR_PG_CFG attribute to be returned with the patch
below TX or RX variants are returned.

commit 7be99413
Author: Thomas Graf <tgraf@suug.ch>
Date:   Wed Jun 13 02:54:55 2012 +0000

    dcbnl: Shorten all command handling functions

This patch reverts this behavior and returns DCB_ATTR_PG_CFG

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Acked-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>