MAINTAINERS: Fix an entry using spaces instead of tabs

In the MAINTAINERS file, names and emails are separated by tabs.  One of
the entries recently added used spaces.  This patch corrects this.

The check-MAINTAINERS.py script breaks a bit when this happens.  This
patch also adds warning about this situation into the script.

ChangeLog:

	* MAINTAINERS: Use tabs between name and email.

contrib/ChangeLog:

	* check-MAINTAINERS.py: Add warning about not using tabs.

Signed-off-by: Filip Kastl <fkastl@suse.cz>