net/phy: enable get_phy_id redefinable

As some PHYs have non-standard PHY ID registers, PHY Id can't
be read correctly by current get_phy_id function, so we enable
get_phy_id redefinable to permit specific PHY driver having own
specific get_phy_id function.

Signed-off-by: Shengzhou Liu <Shengzhou.Liu@freescale.com>

drivers/net/phy/phy.c

@@ -18,6 +18,7 @@
 #include <phy.h>
 #include <errno.h>
 #include <linux/err.h>
+#include <linux/compiler.h>
 
 /* Generic PHY support and helper functions */
 
@@ -577,7 +578,7 @@ static struct phy_device *phy_device_create(struct mii_dev *bus, int addr,
  * Description: Reads the ID registers of the PHY at @addr on the
  *   @bus, stores it in @phy_id and returns zero on success.
  */
-static int get_phy_id(struct mii_dev *bus, int addr, int devad, u32 *phy_id)
+int __weak get_phy_id(struct mii_dev *bus, int addr, int devad, u32 *phy_id)
 {
 	int phy_reg;