pico-imx6ul: MAINTAINERS: Add pico-dwarf entry

pico-dwarf-imx6ul_defconfig does not have an entry in MAINTAINERS file,
so add it to avoid a build warning.

Reported-by: Stefano Babic <sbabic@denx.de>
Signed-off-by: Fabio Estevam <festevam@gmail.com>
diff --git a/board/technexion/pico-imx6ul/MAINTAINERS b/board/technexion/pico-imx6ul/MAINTAINERS
index a662ff4..e9b5a97 100644
--- a/board/technexion/pico-imx6ul/MAINTAINERS
+++ b/board/technexion/pico-imx6ul/MAINTAINERS
@@ -5,5 +5,6 @@
 F:	board/technexion/pico-imx6ul/
 F:	include/configs/pico-imx6ul.h
 F:	configs/pico-imx6ul_defconfig
+F:	configs/pico-dwarf-imx6ul_defconfig
 F:	configs/pico-hobbit-imx6ul_defconfig
 F:	configs/pico-pi-imx6ul_defconfig