ARC: stack unwinder to bail if PC is not kernel mode

Currently, it doesn't invoke the callback but continues to unwind

Also while at it - simplify the code a bit
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/kernel/stacktrace.c

@@ -122,19 +122,17 @@ arc_unwind_core(struct task_struct *tsk, struct pt_regs *regs,
 	while (1) {
 		address = UNW_PC(&frame_info);
 
-		if (address && __kernel_text_address(address)) {
+		if (!address || !__kernel_text_address(address))
+			break;
+
 		if (consumer_fn(address, arg) == -1)
 			break;
-		}
 
 		ret = arc_unwind(&frame_info);
+		if (ret)
+			break;
 
-		if (ret == 0) {
 		frame_info.regs.r63 = frame_info.regs.r31;
-			continue;
-		} else {
-			break;
-		}
 	}
 
 	return address;		/* return the last address it saw */