ARC: [intc-compact] simplify code for 2 priority levels

ARC700 support for 2 interrupt priorities historically allowed even slow
perpherals such as emac and uart to setup high priority interrupts
which was wrong from the beginning as they could possibly delay the more
critical timer interrupt.

The hardware support for 2 level interrupts in ARCompact is less than
ideal anyways (judging from the "hacks" in low level entry code and thus
is not used in productions systems I know of.

So reduce the scope of this to timer only, thereby reducing a bunch of
complexity.

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

arch/arc/kernel/entry-compact.S

@@ -91,27 +91,13 @@ VECTOR   mem_service             ; 0x8, Mem exception   (0x1)
 VECTOR   instr_service           ; 0x10, Instrn Error   (0x2)
 
 ; ******************** Device ISRs **********************
-#ifdef CONFIG_ARC_IRQ3_LV2
+#ifdef CONFIG_ARC_COMPACT_IRQ_LEVELS
 VECTOR   handle_interrupt_level2
 #else
 VECTOR   handle_interrupt_level1
 #endif
 
-VECTOR   handle_interrupt_level1
-
-#ifdef CONFIG_ARC_IRQ5_LV2
-VECTOR   handle_interrupt_level2
-#else
-VECTOR   handle_interrupt_level1
-#endif
-
-#ifdef CONFIG_ARC_IRQ6_LV2
-VECTOR   handle_interrupt_level2
-#else
-VECTOR   handle_interrupt_level1
-#endif
-
-.rept   25
+.rept   28
 VECTOR   handle_interrupt_level1 ; Other devices
 .endr