MAINTAINERS: Update Peng Fan's email address

Use Peng Fan's new NXP email address in MAINTAINERS files.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Acked-by: Peng Fan <peng.fan@nxp.com>

board/freescale/mx6qsabreauto/MAINTAINERS

 MX6QSABREAUTO BOARD
 M:	Fabio Estevam <fabio.estevam@nxp.com>
-M:	Peng Fan <Peng.Fan@freescale.com>
+M:	Peng Fan <peng.fan@nxp.com>
 S:	Maintained
 F:	board/freescale/mx6qsabreauto/
 F:	include/configs/mx6qsabreauto.h

board/freescale/mx6slevk/MAINTAINERS

 MX6SLEVK BOARD
 M:	Fabio Estevam <fabio.estevam@nxp.com>
-M:	Peng Fan <Peng.Fan@freescale.com>
+M:	Peng Fan <peng.fan@nxp.com>
 S:	Maintained
 F:	board/freescale/mx6slevk/
 F:	include/configs/mx6slevk.h

board/freescale/mx6ul_14x14_evk/MAINTAINERS

 MX6ULEVK BOARD
-M:	Peng Fan <Peng.Fan@freescale.com>
+M:	Peng Fan <peng.fan@nxp.com>
 S:	Maintained
 F:	board/freescale/mx6ul_14x14_evk/
 F:	include/configs/mx6ul_14x14_evk.h