imx:mx6slevk add spi nor boot support

Add spi nor boot support for mx6slevk board.

Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
Reviewed-by: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com>
diff --git a/board/freescale/mx6slevk/MAINTAINERS b/board/freescale/mx6slevk/MAINTAINERS
index 660af91..18d31a8 100644
--- a/board/freescale/mx6slevk/MAINTAINERS
+++ b/board/freescale/mx6slevk/MAINTAINERS
@@ -4,3 +4,4 @@
 F:	board/freescale/mx6slevk/
 F:	include/configs/mx6slevk.h
 F:	configs/mx6slevk_defconfig
+F:	configs/mx6slevk_spinor_defconfig