ARCv2: entry: rewrite to enable use of double load/stores LDD/STD

- the motivation was to be remove blatent copy-paste due to hasty support
   of CONFIG_ARC_IRQ_NO_AUTOSAVE support

 - but with refactoring we could use LDD/STD to greatly optimize the code

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/kernel/entry-arcv2.S

@@ -67,7 +67,7 @@ reserved:
 
 ENTRY(handle_interrupt)
 
-	INTERRUPT_PROLOGUE  irq
+	INTERRUPT_PROLOGUE
 
 	# irq control APIs local_irq_save/restore/disable/enable fiddle with
 	# global interrupt enable bits in STATUS32 (.IE for 1 prio, .E[] for 2 prio)
@@ -223,7 +223,7 @@ debug_marker_l1:
 	bset.nz	r11, r11, AUX_IRQ_ACT_BIT_U	; NZ means U
 	sr	r11, [AUX_IRQ_ACT]
 
-	INTERRUPT_EPILOGUE  irq
+	INTERRUPT_EPILOGUE
 	rtie
 
 ;####### Return from Exception / pure kernel mode #######