MAINTAINERS: add NXP linux team maillist as i.MX reviewer

Add NXP linux team upstream maillist as reviewer
Signed-off-by: NPeng Fan <peng.fan@nxp.com>

MAINTAINERS

@@ -121,6 +121,7 @@ F:	drivers/spi/bcmstb_spi.c
 ARM FREESCALE IMX
 M:	Stefano Babic <sbabic@denx.de>
 M:	Fabio Estevam <fabio.estevam@nxp.com>
+R:	NXP Linux Team <linux-imx@nxp.com>
 S:	Maintained
 T:	git git://git.denx.de/u-boot-imx.git
 F:	arch/arm/cpu/arm1136/mx*/