ARC Fix for 4.7-rc6

- Reinstate dwarf unwinder/loadable-modules with new gnu tools
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Merge tag 'arc-4.7-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc

Pull ARC fix from Vineet Gupta:
 "Reinstate dwarf unwinder/loadable-modules with new gnu tools"

* tag 'arc-4.7-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc:
  arc: unwind: warn only once if DW2_UNWIND is disabled
  ARC: unwind: ensure that .debug_frame is generated (vs. .eh_frame)

arch/arc/Makefile

@@ -66,8 +66,6 @@ endif
 
 endif
 
-cflags-$(CONFIG_ARC_DW2_UNWIND)		+= -fasynchronous-unwind-tables
-
 # By default gcc 4.8 generates dwarf4 which kernel unwinder can't grok
 ifeq ($(atleast_gcc48),y)
 cflags-$(CONFIG_ARC_DW2_UNWIND)		+= -gdwarf-2

arch/arc/kernel/stacktrace.c

@@ -142,7 +142,7 @@ arc_unwind_core(struct task_struct *tsk, struct pt_regs *regs,
 	 * prelogue is setup (callee regs saved and then fp set and not other
 	 * way around
 	 */
-	pr_warn("CONFIG_ARC_DW2_UNWIND needs to be enabled\n");
+	pr_warn_once("CONFIG_ARC_DW2_UNWIND needs to be enabled\n");
 	return 0;
 
 #endif