ARM: 8918/2: only build return_address() if needed

The system currently warns if the config conditions for
building return_address in arch/arm/kernel/return_address.c
are not met, leaving just an EXPORT_SYMBOL_GPL(return_address)
of a function defined to be 'static linline'.
This is a result of aeea3592 ("ARM: 8158/1: LLVMLinux: use static inline in ARM ftrace.h").

Since we're not going to build anything other than an exported
symbol for something that is already being defined to be an
inline-able return of NULL, just avoid building the code to
remove the following warning:

Fixes: aeea3592 ("ARM: 8158/1: LLVMLinux: use static inline in ARM ftrace.h")
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

arch/arm/kernel/Makefile

@@ -17,10 +17,14 @@ CFLAGS_REMOVE_return_address.o = -pg
 # Object file lists.
 
 obj-y		:= elf.o entry-common.o irq.o opcodes.o \
-		   process.o ptrace.o reboot.o return_address.o \
+		   process.o ptrace.o reboot.o \
 		   setup.o signal.o sigreturn_codes.o \
 		   stacktrace.o sys_arm.o time.o traps.o
 
+ifneq ($(CONFIG_ARM_UNWIND),y)
+obj-$(CONFIG_FRAME_POINTER)	+= return_address.o
+endif
+
 obj-$(CONFIG_ATAGS)		+= atags_parse.o
 obj-$(CONFIG_ATAGS_PROC)	+= atags_proc.o
 obj-$(CONFIG_DEPRECATED_PARAM_STRUCT) += atags_compat.o

arch/arm/kernel/return_address.c

@@ -7,8 +7,6 @@
  */
 #include <linux/export.h>
 #include <linux/ftrace.h>
-
-#if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
 #include <linux/sched.h>
 
 #include <asm/stacktrace.h>
@@ -53,6 +51,4 @@ void *return_address(unsigned int level)
 		return NULL;
 }
 
-#endif /* if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) */
-
 EXPORT_SYMBOL_GPL(return_address);