powerpc/85xx: Rework MPC8536 SERDES is_serdes_configured support

Move serdes init until after we are in ram so we can keep track of a
global static protocal map for the particular serdes config we are in.
This makes is_serdes_configured() much simplier and not constantly
reading registers to determine if a given device is enabled based on the
protocol.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/include/configs/MPC8536DS.h b/include/configs/MPC8536DS.h
index 24a75c6..890a6c9 100644
--- a/include/configs/MPC8536DS.h
+++ b/include/configs/MPC8536DS.h
@@ -65,6 +65,7 @@
 #define CONFIG_FSL_PCI_INIT	1	/* Use common FSL init code */
 #define CONFIG_FSL_PCIE_RESET	1	/* need PCIe reset errata */
 #define CONFIG_SYS_PCI_64BIT	1	/* enable 64-bit PCI resources */
+#define CONFIG_SYS_HAS_SERDES		/* has SERDES */
 
 #define CONFIG_FSL_LAW		1	/* Use common FSL init code */
 #define CONFIG_E1000		1	/* Defind e1000 pci Ethernet card*/