r8169: fix a bug in rtl8169_init_phy()

commit 54405cde (r8169: support control of advertising.)
introduced a bug in rtl8169_init_phy()

Reported-by: Piotr Hosowicz <piotr@hosowicz.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Oliver Neukum <oliver@neukum.org>
Cc: Francois Romieu <romieu@fr.zoreil.com>
Tested-by: Anca Emanuel <anca.emanuel@gmail.com>
Tested-by: Piotr Hosowicz <piotr@hosowicz.com>
Signed-off-by: David S. Miller <davem@davemloft.net>