docs: kabi: helpers: add helper for debug bits 7 and 8

The kabi logic supports 8 debug bits, but only 6 are currently
documented. Document the remaining ones.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <60e99b9060396eac8621954d6b8a73af45df90fb.1768838938.git.mchehab+huawei@kernel.org>

Author: mchehab

tools/lib/python/abi/helpers.py

@@ -35,4 +35,6 @@ class AbiDebug:
 16 - enable debug for what to regex conversion
 32 - enable debug for symbol regex subgroups
 64 - enable debug for sysfs graph tree variable
+128 - enable debug of search groups
+256 - enable displaying refrence tree graphs for undefined symbols.
 """