add Marvell tools to maintained sources list

Declate Marvell's ownership on tools/doimage

Signed-off-by: Konstantin Porotchkin <kostap@marvell.com>
diff --git a/maintainers.rst b/maintainers.rst
index 383e47b..cb4f420 100644
--- a/maintainers.rst
+++ b/maintainers.rst
@@ -81,6 +81,7 @@
 :F: docs/plat/marvell/
 :F: plat/marvell/
 :F: drivers/marvell/
+:F: tools/doimage/
 
 NVidia platform ports
 ---------------------