netconsole: improve code style in parser function

Split assignment from conditional checks and use preferred null pointer
check style (!delim instead of == NULL) in netconsole_parser_cmdline().
This improves code readability and follows kernel coding style
conventions.

Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20250613-rework-v3-6-0752bf2e6912@debian.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>