Fix man page entry for Icarus Verilog documentation

(cherry picked from commit d3bda52d69)

Documentation/conf.py

@@ -142,7 +142,7 @@ latex_documents = [
 # One entry per manual page. List of tuples
 # (source start file, name, description, authors, manual section).
 man_pages = [
-    (master_doc, 'iverilog', 'Icarus Verilog Documentation',
+    (master_doc, 'iverilog-docs', 'Icarus Verilog Documentation',
      [author], 1)
 ]