imx: boards: Add maintainers info

Add MAINTAINERS info for mx6slevk_spl, mx6ul_9x9_evk and mx6qpsabreauto.

Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
Cc: Stefano Babic <sbabic@denx.de>
diff --git a/board/freescale/mx6ul_14x14_evk/MAINTAINERS b/board/freescale/mx6ul_14x14_evk/MAINTAINERS
index 611feca..d5f74b7 100644
--- a/board/freescale/mx6ul_14x14_evk/MAINTAINERS
+++ b/board/freescale/mx6ul_14x14_evk/MAINTAINERS
@@ -4,3 +4,4 @@
 F:	board/freescale/mx6ul_14x14_evk/
 F:	include/configs/mx6ul_14x14_evk.h
 F:	configs/mx6ul_14x14_evk_defconfig
+F:	configs/mx6ul_9x9_evk_defconfig