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/arch/arm/Kconfig b/arch/arm/Kconfig
index bd802b3..5864646 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -576,7 +576,7 @@
 	select CPU_ARM926EJS
 	select SUPPORT_SPL
 
-config ORION5X
+config ARCH_ORION5X
 	bool "Marvell Orion"
 	select CPU_ARM926EJS
 
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 5d32dec..2b44ffb 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -67,8 +67,7 @@
 machine-$(CONFIG_ARCH_MESON)		+= meson
 machine-$(CONFIG_ARCH_MVEBU)		+= mvebu
 machine-$(CONFIG_ARCH_OMAP2PLUS)	+= omap2
-# TODO: rename CONFIG_ORION5X -> CONFIG_ARCH_ORION5X
-machine-$(CONFIG_ORION5X)		+= orion5x
+machine-$(CONFIG_ARCH_ORION5X)		+= orion5x
 machine-$(CONFIG_ARCH_OWL)		+= owl
 machine-$(CONFIG_ARCH_RMOBILE)		+= rmobile
 machine-$(CONFIG_ARCH_ROCKCHIP)		+= rockchip
diff --git a/arch/arm/mach-orion5x/Kconfig b/arch/arm/mach-orion5x/Kconfig
index 7644b8d..5baa6fb 100644
--- a/arch/arm/mach-orion5x/Kconfig
+++ b/arch/arm/mach-orion5x/Kconfig
@@ -1,4 +1,4 @@
-if ORION5X
+if ARCH_ORION5X
 
 choice
 	prompt "Marvell Orion board select"