board: amlogic: add mailing-list to MAINTAINERS

Add missing mailing-list to the amlogic boards MAINTAINERS file.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
diff --git a/board/amlogic/u200/MAINTAINERS b/board/amlogic/u200/MAINTAINERS
index baf3813..5ae7f5e 100644
--- a/board/amlogic/u200/MAINTAINERS
+++ b/board/amlogic/u200/MAINTAINERS
@@ -1,5 +1,6 @@
 U200
 M:	Neil Armstrong <narmstrong@baylibre.com>
 S:	Maintained
+L:	u-boot-amlogic@groups.io
 F:	board/amlogic/u200/
 F:	configs/u200_defconfig