irqchip: Add COMPILE_TEST support for IMX_INTMUX

Add COMPILE_TEST support to IMX_INTMUX driver for better compile
testing coverage.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/1583588547-7164-1-git-send-email-Anson.Huang@nxp.com

drivers/irqchip/Kconfig

@@ -458,7 +458,7 @@ config IMX_IRQSTEER
 	  Support for the i.MX IRQSTEER interrupt multiplexer/remapper.
 
 config IMX_INTMUX
-	def_bool y if ARCH_MXC
+	def_bool y if ARCH_MXC || COMPILE_TEST
 	select IRQ_DOMAIN
 	help
 	  Support for the i.MX INTMUX interrupt multiplexer.