MAINTAINERS: add ARM/FREESCALE MXS entry

As suggested by Pengutronix, they want to get Sascha relieved from
the burden of maintaining MXS sub-architecture.  Since I brought the
most of MXS core code to mainline (with the great help from
Pengutronix people, thanks!), I would like to step up for maintaining
MXS.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>

MAINTAINERS

@@ -804,6 +804,13 @@ S:	Maintained
 T:	git git://git.linaro.org/people/shawnguo/linux-2.6.git
 F:	arch/arm/mach-imx/*imx6*
 
+ARM/FREESCALE MXS ARM ARCHITECTURE
+M:	Shawn Guo <shawn.guo@linaro.org>
+L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
+S:	Maintained
+T:	git git://git.linaro.org/people/shawnguo/linux-2.6.git
+F:	arch/arm/mach-mxs/
+
 ARM/GLOMATION GESBC9312SX MACHINE SUPPORT
 M:	Lennert Buytenhek <kernel@wantstofly.org>
 L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)