docs: kdoc_re: better represent long regular expressions

docs: kdoc_re: better represent long regular expressions

The Sphinx output from autodoc doesn't automatically break long
lines, except on spaces.

Change KernRe __repr__() to break the pattern on multiple strings,
each one with a maximum limit of 60 characters.

With that, documentation output for KernRe should now be displayable,
even on long strings.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <60c264a9d277fed655b1a62df2195562c8596090.1773823995.git.mchehab+huawei@kernel.org>