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/avionic-design/tec/MAINTAINERS b/board/avionic-design/tec/MAINTAINERS
index 10f1aac..36088e7 100644
--- a/board/avionic-design/tec/MAINTAINERS
+++ b/board/avionic-design/tec/MAINTAINERS
@@ -2,5 +2,6 @@
 M:	Alban Bedel <alban.bedel@avionic-design.de>
 S:	Maintained
 F:	board/avionic-design/tec/
+F:	board/avionic-design/common/
 F:	include/configs/tec.h
 F:	configs/tec_defconfig