ARCv2: intc: untangle SMP, MCIP and IDU

The IDU intc is technically part of MCIP (Multi-core IP) hence
historically was only available in a SMP hardware build (and thus only
in a SMP kernel build). Now that hardware restriction has been lifted,
so a UP kernel needs to support it.

This requires breaking mcip.c into parts which are strictly SMP
(inter-core interrupts) and IDU which in reality is just another
intc and thus has no bearing on SMP.

This change allows IDU in UP builds and with a suitable device tree, we
can have the cascaded intc system

    ARCv2 core intc <---> ARCv2 IDU intc <---> periperals

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index ecd1237..6f67895 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -186,14 +186,6 @@
 config ARC_HAS_COH_CACHES
 	def_bool n
 
-config ARC_MCIP
-	bool "ARConnect Multicore IP (MCIP) Support "
-	depends on ISA_ARCV2
-	help
-	  This IP block enables SMP in ARC-HS38 cores.
-	  It provides for cross-core interrupts, multi-core debug
-	  hardware semaphores, shared memory,....
-
 config NR_CPUS
 	int "Maximum number of CPUs (2-4096)"
 	range 2 4096
@@ -211,6 +203,15 @@
 
 endif	#SMP
 
+config ARC_MCIP
+	bool "ARConnect Multicore IP (MCIP) Support "
+	depends on ISA_ARCV2
+	default y if SMP
+	help
+	  This IP block enables SMP in ARC-HS38 cores.
+	  It provides for cross-core interrupts, multi-core debug
+	  hardware semaphores, shared memory,....
+
 menuconfig ARC_CACHE
 	bool "Enable Cache Support"
 	default y