docs: kdoc: remove the brcount floor in process_proto_type()

docs: kdoc: remove the brcount floor in process_proto_type()

Putting the floor under brcount does not change the output in any way, just
remove it.

Change the termination test from ==0 to <=0 to prevent infinite loops in
case somebody does something truly wacko in the code.

Reviewed-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Tested-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20250703184403.274408-4-corbet@lwn.net