MAINTAINERS: update Shawn's email to use kernel.org one

Update my mailbox to use kernel.org one for handling kernel community
maintenance traffic.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Kevin Hilman <khilman@linaro.org>

MAINTAINERS

@@ -1035,7 +1035,7 @@ F:	arch/arm/include/asm/hardware/dec21285.h
 F:	arch/arm/mach-footbridge/
 
 ARM/FREESCALE IMX / MXC ARM ARCHITECTURE
-M:	Shawn Guo <shawn.guo@linaro.org>
+M:	Shawn Guo <shawnguo@kernel.org>
 M:	Sascha Hauer <kernel@pengutronix.de>
 L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
 S:	Maintained
@@ -1048,7 +1048,7 @@ F:	drivers/clk/imx/
 F:	include/soc/imx/
 
 ARM/FREESCALE VYBRID ARM ARCHITECTURE
-M:	Shawn Guo <shawn.guo@linaro.org>
+M:	Shawn Guo <shawnguo@kernel.org>
 M:	Sascha Hauer <kernel@pengutronix.de>
 R:	Stefan Agner <stefan@agner.ch>
 L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)