docs/system/arm: Add placeholder docs for mcimx6ul-evk and mcimx7d-sabre

Add placeholder docs for the mcimx6ul-evk and mcimx7d-sabre boards.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20241018141332.942844-7-peter.maydell@linaro.org
diff --git a/MAINTAINERS b/MAINTAINERS
index 66c7572..1e88b57 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -791,6 +791,7 @@
 F: hw/misc/imx6ul_ccm.c
 F: include/hw/arm/fsl-imx6ul.h
 F: include/hw/misc/imx6ul_ccm.h
+F: docs/system/arm/mcimx6ul-evk.rst
 
 MCIMX7D SABRE / i.MX7
 M: Peter Maydell <peter.maydell@linaro.org>
@@ -804,6 +805,7 @@
 F: include/hw/misc/imx7_*.h
 F: hw/pci-host/designware.c
 F: include/hw/pci-host/designware.h
+F: docs/system/arm/mcimx7d-sabre.rst
 
 MPS2 / MPS3
 M: Peter Maydell <peter.maydell@linaro.org>