ARM: make arch_ret_to_user macro optional

Only 3 platforms need arch_ret_to_user macro, so add ARCH_HAS_RET_TO_USER
kconfig option and make iop13xx, iop32x and iop33x select it.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index a48aecc..7d809b7 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -186,6 +186,9 @@
 config FIQ
 	bool
 
+config NEED_RET_TO_USER
+	bool
+
 config ARCH_MTD_XIP
 	bool
 
@@ -479,6 +482,7 @@
 	select ARCH_SUPPORTS_MSI
 	select VMSPLIT_1G
 	select NEED_MACH_MEMORY_H
+	select NEED_RET_TO_USER
 	help
 	  Support for Intel's IOP13XX (XScale) family of processors.
 
@@ -486,6 +490,7 @@
 	bool "IOP32x-based"
 	depends on MMU
 	select CPU_XSCALE
+	select NEED_RET_TO_USER
 	select PLAT_IOP
 	select PCI
 	select ARCH_REQUIRE_GPIOLIB
@@ -497,6 +502,7 @@
 	bool "IOP33x-based"
 	depends on MMU
 	select CPU_XSCALE
+	select NEED_RET_TO_USER
 	select PLAT_IOP
 	select PCI
 	select ARCH_REQUIRE_GPIOLIB