mx6ullevk: Add missing MAINTAINERS for mx6ull_14x14_evk_plugin_defconfig

Add 'Peng Fan' as MAINTAINERS of configs/mx6ull_14x14_evk_plugin_defconfig
which is missing in below commit
"imx: mx6ull_14x14_evk: add plugin defconfig"
(sha1: b90ebf49)

Cc: Stefano Babic <sbabic@denx.de>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Jagan Teki <jagan@openedev.com>

board/freescale/mx6ullevk/MAINTAINERS

@@ -4,3 +4,4 @@ S:	Maintained
 F:	board/freescale/mx6ullevk/
 F:	include/configs/mx6ullevk.h
 F:	configs/mx6ull_14x14_evk_defconfig
+F:	configs/mx6ull_14x14_evk_plugin_defconfig