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>

arch/arm/Kconfig

@@ -186,6 +186,9 @@ config GENERIC_ISA_DMA
 config FIQ
 	bool
 
+config NEED_RET_TO_USER
+	bool
+
 config ARCH_MTD_XIP
 	bool
 
@@ -479,6 +482,7 @@ config ARCH_IOP13XX
 	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 @@ config ARCH_IOP32X
 	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 @@ config ARCH_IOP33X
 	bool "IOP33x-based"
 	depends on MMU
 	select CPU_XSCALE
+	select NEED_RET_TO_USER
 	select PLAT_IOP
 	select PCI
 	select ARCH_REQUIRE_GPIOLIB

arch/arm/kernel/entry-common.S

@@ -10,9 +10,15 @@
 
 #include <asm/unistd.h>
 #include <asm/ftrace.h>
-#include <mach/entry-macro.S>
 #include <asm/unwind.h>
 
+#ifdef CONFIG_NEED_RET_TO_USER
+#include <mach/entry-macro.S>
+#else
+	.macro  arch_ret_to_user, tmp1, tmp2
+	.endm
+#endif
+
 #include "entry-header.S"