rename symbol: CONFIG_ORION5X -> CONFIG_ARCH_ORION5X

Have this symbol follow the pattern of all other such symbols.
This patch removes a TODO from the code.

Signed-off-by: Trevor Woerner <twoerner@gmail.com>
diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index 38f2bd6..4d6716f 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -309,7 +309,7 @@
 
 config MVGBE
 	bool "Marvell Orion5x/Kirkwood network interface support"
-	depends on KIRKWOOD || ORION5X
+	depends on KIRKWOOD || ARCH_ORION5X
 	select PHYLIB if DM_ETH
 	help
 	  This driver supports the network interface units in the
diff --git a/drivers/net/mvgbe.c b/drivers/net/mvgbe.c
index 037e59e..b0b8d34 100644
--- a/drivers/net/mvgbe.c
+++ b/drivers/net/mvgbe.c
@@ -26,7 +26,7 @@
 
 #if defined(CONFIG_KIRKWOOD)
 #include <asm/arch/soc.h>
-#elif defined(CONFIG_ORION5X)
+#elif defined(CONFIG_ARCH_ORION5X)
 #include <asm/arch/orion5x.h>
 #endif