docs: kernel_feat.py: fix build error for missing files

If the directory passed to the '.. kernel-feat::' directive does not
exist or the get_feat.pl script does not find any files to extract
features from, Sphinx will report the following error:

    Sphinx parallel build error:
    UnboundLocalError: local variable 'fname' referenced before assignment
    make[2]: *** [Documentation/Makefile:102: htmldocs] Error 2

This is due to how I changed the script in c48a7c4 ("docs:
kernel_feat.py: fix potential command injection"). Before that, the
filename passed along to self.nestedParse() in this case was weirdly
just the whole get_feat.pl invocation.

We can fix it by doing what kernel_abi.py does -- just pass
self.arguments[0] as 'fname'.

Fixes: c48a7c4 ("docs: kernel_feat.py: fix potential command injection")
Cc: Justin Forbes <[email protected]>
Cc: Salvatore Bonaccorso <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: Mauro Carvalho Chehab <[email protected]>
Cc: [email protected]
Signed-off-by: Vegard Nossum <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jonathan Corbet <[email protected]>

Documentation/sphinx/kernel_feat.py

@@ -109,7 +109,7 @@ def run(self):
             else:
                 out_lines += line + "\n"
 
-        nodeList = self.nestedParse(out_lines, fname)
+        nodeList = self.nestedParse(out_lines, self.arguments[0])
         return nodeList
 
     def nestedParse(self, lines, fname):