MAINTAINERS: Add missing directory

arch/arm/mach-imx/ is part of the i.MX support. Add it.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
diff --git a/MAINTAINERS b/MAINTAINERS
index 071a996..c9ae02a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -789,6 +789,7 @@
 S:	Maintained
 T:	git git://git.pengutronix.de/git/imx/linux-2.6.git
 F:	arch/arm/mach-mx*/
+F:	arch/arm/mach-imx/
 F:	arch/arm/plat-mxc/
 
 ARM/FREESCALE IMX51