phy: add phy_smsc_init() declaration

This trivial change removes a compilation warning:
  ----8<----
  phy.c: In function 'phy_init':
  phy.c:448:2: warning: implicit declaration of function 'phy_smsc_init'
  ----8<----

Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
Cc: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>
Acked-by: Marek Vasut <marek.vasut@gmail.com>

include/phy.h

@@ -224,6 +224,7 @@ int phy_marvell_init(void);
 int phy_micrel_init(void);
 int phy_natsemi_init(void);
 int phy_realtek_init(void);
+int phy_smsc_init(void);
 int phy_teranetics_init(void);
 int phy_vitesse_init(void);