style: Move the last bits of file_types.py to the style package

style: Move the last bits of file_types.py to the style package

The commit that refactored the style checkers into a new Python
package (style: Refactor the style checker as a Python package)
accidentally left a fragment of file_types.py in the old location
(util/style.py). This was caused by a race between the commit that
moved the file and Nate's commit that added a copyright header to the
file.

This commit moves the last fragment (the copyright header) and removes
the old file.

Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
--HG--
extra : amend_source : 946f1f6fee034ae79bd50ea7dfc3299a60f070c0