patch-list: Limit the number of chars to 100 for the patch subject

It can happen that people send a patch with a huge subject, by mistake.
Make sure it can interfere too much with the list of patches.

As an email subject can include extra words compared to a patch subject
(list header, tags, ...) let's have a slightly larger limit than 72 or
80.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>