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/BuR/brppt2/MAINTAINERS b/board/BuR/brppt2/MAINTAINERS
index fe65188..bfeaa57 100644
--- a/board/BuR/brppt2/MAINTAINERS
+++ b/board/BuR/brppt2/MAINTAINERS
@@ -2,5 +2,6 @@
 M:	Wolfgang Wallner <wolfgang.wallner@br-automation.com>
 S:	Maintained
 F:	board/BuR/brppt2/
+F:	board/BuR/common/
 F:	include/configs/brppt2.h
 F:	configs/brppt2_defconfig