MAINTAINERS: Add a number of "common" directories

A number of platforms have "common" directories that are in turn not
listed by the board MAINTAINERS file.  Add these directories in many
cases.

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/board/toradex/colibri_t20/MAINTAINERS b/board/toradex/colibri_t20/MAINTAINERS
index 77c2fc3..d0c5b11 100644
--- a/board/toradex/colibri_t20/MAINTAINERS
+++ b/board/toradex/colibri_t20/MAINTAINERS
@@ -2,6 +2,7 @@
 M:	Marcel Ziswiler <marcel.ziswiler@toradex.com>
 S:	Maintained
 F:	board/toradex/colibri_t20/
+F:	board/toradex/common/
 F:	include/configs/colibri_t20.h
 F:	configs/colibri_t20_defconfig
 F:	arch/arm/dts/tegra20-colibri.dtb