Fixup SGMII PHY ids in the device tree

The device tree's PHY addresses need to be fixed up if we're using the
SGMII Riser Card.

The 8572, 8536, and 8544 DS boards were modified to call this function.

Code idea taken from Liu Yu <yu.liu@freescale.com>

Signed-off-by: Andy Fleming <afleming@freescale.com>
diff --git a/board/freescale/common/sgmii_riser.h b/board/freescale/common/sgmii_riser.h
index 8d56a1f..e1fcc85 100644
--- a/board/freescale/common/sgmii_riser.h
+++ b/board/freescale/common/sgmii_riser.h
@@ -13,3 +13,4 @@
  */
 
 void fsl_sgmii_riser_init(struct tsec_info_struct *tsec_info, int num);
+void fsl_sgmii_riser_fdt_fixup(void *fdt);