ARCv2: make unimplemented vectors as no-ops rather than halt core

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
diff --git a/arch/arc/kernel/entry-arcv2.S b/arch/arc/kernel/entry-arcv2.S
index 2585632..cc558a2 100644
--- a/arch/arc/kernel/entry-arcv2.S
+++ b/arch/arc/kernel/entry-arcv2.S
@@ -100,15 +100,21 @@
 ;################### Non TLB Exception Handling #############################
 
 ENTRY(EV_SWI)
-	flag 1
+	; TODO: implement this
+	EXCEPTION_PROLOGUE
+	b   ret_from_exception
 END(EV_SWI)
 
 ENTRY(EV_DivZero)
-	flag 1
+	; TODO: implement this
+	EXCEPTION_PROLOGUE
+	b   ret_from_exception
 END(EV_DivZero)
 
 ENTRY(EV_DCError)
-	flag 1
+	; TODO: implement this
+	EXCEPTION_PROLOGUE
+	b   ret_from_exception
 END(EV_DCError)
 
 ; ---------------------------------------------