[tlgen] Remove start/end markers from autogenerated doc

I don't think these notes are really needed: our document generation
flow dumps this stuff to a separate markdown fragment file anyway, so
it's not particularly difficult to understand what's going on. Also,
they were appearing in the rendered documentation, which is definitely
wrong.

Signed-off-by: Rupert Swarbrick <rswarbrick@lowrisc.org>
diff --git a/util/tlgen/doc.py b/util/tlgen/doc.py
index 5c0037d..6747df0 100644
--- a/util/tlgen/doc.py
+++ b/util/tlgen/doc.py
@@ -11,8 +11,6 @@
 
 doc_intro = """
 
-(start of output generated by `{}`)
-
 The tables describe each key and the type of the value. The following
 types are used:
 
@@ -20,12 +18,6 @@
 ---- | -----------
 """
 
-doc_tail = """
-
-(end of output generated by `{}`)
-
-"""
-
 
 def print_control(control, heading):
     """Print a control group and its subgroup recursively
@@ -82,7 +74,7 @@
 def selfdoc(heading, cmd=""):
     # heading : Markdown header depth
     # value type
-    outstr = doc_intro.format(cmd)
+    outstr = doc_intro
 
     for k, v in val_types.items():
         outstr += v[0] + " | " + v[1] + "\n"
@@ -91,6 +83,5 @@
     outstr += print_control(root, heading)
 
     # connections: Needs custom as the key are hosts (can vary)
-    outstr += doc_tail.format(cmd)
 
     return outstr