board: amlogic: add board doc files to MAINTAINERS

Add the recently added reStructuredText board documentation in the
appropriate MAINTAINERS files.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
diff --git a/board/amlogic/p200/MAINTAINERS b/board/amlogic/p200/MAINTAINERS
index c20f056..1df9b8b 100644
--- a/board/amlogic/p200/MAINTAINERS
+++ b/board/amlogic/p200/MAINTAINERS
@@ -7,3 +7,6 @@
 F:	configs/nanopi-k2_defconfig
 F:	configs/odroid-c2_defconfig
 F:	configs/p200_defconfig
+F:	doc/board/amlogic/p200.rst
+F:	doc/board/amlogic/nanopi-k2.rst
+F:	doc/board/amlogic/odroid-c2.rst