xtensa: variant irq set callbacks

Allow the core variant code to provide irq enable/disable callbacks.

Signed-off-by: Johannes Weiner <jw@emlix.com>
Signed-off-by: Chris Zankel <chris@zankel.net>
diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
index cf2501b..705bb71 100644
--- a/arch/xtensa/Kconfig
+++ b/arch/xtensa/Kconfig
@@ -51,6 +51,9 @@
 config MMU
 	def_bool n
 
+config VARIANT_IRQ_SWITCH
+	def_bool n
+
 menu "Processor type and features"
 
 choice