drivers: interrupt_controller: Refactor drivers to use shared init prio

Refactors interrupt controller drivers to use the shared driver class
initialization priority configuration, CONFIG_INTC_INIT_PRIORITY, to
allow configuring interrupt controller drivers separately from other
devices. This is similar to other driver classes.

The default is set to CONFIG_KERNEL_INIT_PRIORITY_DEFAULT to preserve
the existing default initialization priority for most drivers.

Signed-off-by: Maureen Helm <maureen.helm@intel.com>
diff --git a/drivers/interrupt_controller/Kconfig b/drivers/interrupt_controller/Kconfig
index bbabc35..3560dde 100644
--- a/drivers/interrupt_controller/Kconfig
+++ b/drivers/interrupt_controller/Kconfig
@@ -45,6 +45,12 @@
 	help
 	  GRLIB IRQMP and IRQAMP
 
+config INTC_INIT_PRIORITY
+	int "Interrupt controller init priority"
+	default KERNEL_INIT_PRIORITY_DEFAULT
+	help
+	  Interrupt controller device initialization priority.
+
 source "drivers/interrupt_controller/Kconfig.multilevel"
 
 source "drivers/interrupt_controller/Kconfig.loapic"