docs: kdoc_parser: fix variable regexes to work with size_t

docs: kdoc_parser: fix variable regexes to work with size_t

The regular expressions meant to pick variable types are too
naive: they forgot that the type word may contain underlines.

It also means that we need to change the regex which detects
var attributes to handle "const".

Co-developed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <8230715239929cf9d475ab81ca1df7de65d82d06.1772469446.git.mchehab+huawei@kernel.org>