boards: amlogic: update documentation for WeTek Core2

Update the device matrix and add build instructions.

Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
[narmstrong: added wetek-core2.rst to q200 MAINTAINERS and added blank lines to fix build]
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
diff --git a/board/amlogic/q200/MAINTAINERS b/board/amlogic/q200/MAINTAINERS
index be16b51..ba7c12b 100644
--- a/board/amlogic/q200/MAINTAINERS
+++ b/board/amlogic/q200/MAINTAINERS
@@ -9,3 +9,4 @@
 F:	configs/libretech-s912-pc_defconfig
 F:	configs/wetek-core2_defconfig
 F:	doc/board/amlogic/khadas-vim2.rst
+F:	doc/board/amlogic/wetek-core2.rst