docs: parse-headers.py: better handle @var arguments

The kernel-doc markups inside headers may contain @var markups.

With the current rule, this would be converted into:

     \* @:c:type:`DMX_BUFFER_FLAG_DISCONTINUITY_INDICATOR <dmx_buffer_flags>`\:

Fix it adding a non-printed space if needed.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/8d06bb713d6ec8de65179dd93defe479715409b6.1755872208.git.mchehab+huawei@kernel.org

Documentation/sphinx/parse-headers.py

@@ -120,12 +120,12 @@ class ParseHeader:
         },
         # This is the name of the enum itself
         "enum": {
-            "prefix": "",
+            "prefix": "\\ ",
             "suffix": "\\ ",
             "ref_type": ":c:type",
         },
         "struct": {
-            "prefix": "",
+            "prefix": "\\ ",
             "suffix": "\\ ",
             "ref_type": ":c:type",
         },
@@ -390,6 +390,8 @@ class ParseHeader:
 
         # Remove "\ " where not needed: before spaces and at the end of lines
         text = re.sub(r"\\ ([\n ])", r"\1", text)
+        text = re.sub(r" \\ ", " ", text)
+
 
         title = os.path.basename(file_in)