[ARM] mx2: add missing Kconfig dependency

It seems this small label was lost in the last merge. Without it
no CPU type is selected for the MX2 family of processors. And a build
will fail badly...

Signed-off-by: Juergen Beisert <j.beisert@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

arch/arm/mm/Kconfig

@@ -187,7 +187,7 @@ config CPU_ARM926T
 		ARCH_AT91SAM9260 || ARCH_AT91SAM9261 || \
 		ARCH_AT91SAM9263 || ARCH_AT91SAM9RL || \
 		ARCH_AT91SAM9G20 || ARCH_AT91CAP9 || \
-		ARCH_NS9XXX || ARCH_DAVINCI
+		ARCH_NS9XXX || ARCH_DAVINCI || ARCH_MX2
 	default y if ARCH_VERSATILE_PB || MACH_VERSATILE_AB || \
 		ARCH_OMAP730 || ARCH_OMAP16XX || \
 		ARCH_PNX4008 || ARCH_NETX || CPU_S3C2412 || \