board: kontron: pitx-imx8m: Add Kontron pitx-imx8m board support

The Kontron pitx-imx8m is an NXP i.MX8MQ based board in the pITX form factor.

Signed-off-by: Heiko Thiery <heiko.thiery@gmail.com>
diff --git a/doc/board/kontron/index.rst b/doc/board/kontron/index.rst
index 7dfe3d9..cb1906e 100644
--- a/doc/board/kontron/index.rst
+++ b/doc/board/kontron/index.rst
@@ -6,6 +6,7 @@
 .. toctree::
    :maxdepth: 2
 
+   pitx-imx8m
    sl28
    sl-mx6ul
    sl-mx8mm