docs: kdoc_parser: allow __exit in function prototypes

Handle functions that are marked with __exit to prevent warnings:

Documentation/networking/iucv:35: ../net/iucv/iucv.c:1918: WARNING: Error in declarator or parameters
Invalid C declaration: Expecting "(" in parameters. [error at 12]
  void __exit iucv_exit (void)
  ------------^

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20260206065440.2412185-1-rdunlap@infradead.org>

Author: rddunlap

tools/lib/python/kdoc/kdoc_parser.py

@@ -175,6 +175,7 @@
     (KernRe(r"^__FORTIFY_INLINE +"), ""),
     (KernRe(r"__init +"), ""),
     (KernRe(r"__init_or_module +"), ""),
+    (KernRe(r"__exit +"), ""),
     (KernRe(r"__deprecated +"), ""),
     (KernRe(r"__flatten +"), ""),
     (KernRe(r"__meminit +"), ""),