ExifInterface: do not spam stacktrace on invalid format

If we scan a directory with "unsupported" files, we get spam
stacktraces.

This is Debug at best.

Also simplify the error so it doesn't drift out of date with reality.
ExifInterface now supports reading more than just JPEG and RAW files,
see class-level javadoc for the latest list of supported formats.

Change-Id: I18e0b10ad735c9ce5696a2ad79f7551203c39d92