docs: kdoc: simplify the kerneldoc recognition code

docs: kdoc: simplify the kerneldoc recognition code

process_name() looks for the first line of a kerneldoc comment.  It
contains two nearly identical regular expressions, the second of which only
catches six cases in the kernel, all of the form:

  define SOME_MACRO_NAME - description

Simply put the "define" into the regex and discard it, eliminating the loop
and the code to remove it specially.

Note that this still treats these defines as if they were functions, but
that's a separate issue.

There is no change in the generated output.

Reviewed-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20250606163438.229916-5-corbet@lwn.net