ARM: mxc91231: select MXC_AVIC

This fixes:

	arch/arm/kernel/built-in.o: In function `__irq_svc':
	io.c:(.text+0x2e0): undefined reference to `avic_base'
	arch/arm/kernel/built-in.o: In function `__irq_usr':
	io.c:(.text+0x4c8): undefined reference to `avic_base'
	arch/arm/mach-mxc91231/built-in.o: In function `mxc91231_init_irq':
	magx-zn5.c:(.init.text+0x18): undefined reference to `mxc_init_irq'

and was broken by

	c7259df3 (ARM i.MX irq: Compile avic irq code only on SoCs that need it)
Signed-off-by: NUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: NSascha Hauer <s.hauer@pengutronix.de>

arch/arm/plat-mxc/Kconfig

@@ -33,6 +33,7 @@ config ARCH_MX3
 config ARCH_MXC91231
 	bool "MXC91231-based"
 	select CPU_V6
+	select MXC_AVIC
 	help
 	  This enables support for systems based on the Freescale MXC91231 family