scripts/kernel-doc: remove an obscure logic from kernel-doc

Kernel-doc has an obscure logic that uses an external file
to map files via a .tmp_filelist.txt file stored at the current
directory. The rationale for such code predates git time,
as it was added on Kernel v2.4.5.5, with the following description:

# 26/05/2001 - Support for separate source and object trees.
# Return error code.
# Keith Owens <[e-mail]>

from commit 396a6123577d ("v2.4.5.4 -> v2.4.5.5") at the historic
tree:
https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/

Support for separate source and object trees is now done on a different
way via make O=<object>.

There's no logic to create such file, so it sounds to me that this is
just dead code.

So, drop it.

Signed-off-by: Mauro Carvalho Chehab <[e-mail]>
Link: https://lore.kernel.org/r/fd3b28[e-mail]
Signed-off-by: Jonathan Corbet <[e-mail]>

scripts/kernel-doc

···
 my %nosymbol_table = ();
 my $declaration_start_line;
 my ($type, $declaration_name, $return_type);
-my ($newsection, $newcontents, $prototype, $brcount, %source_map);
+my ($newsection, $newcontents, $prototype, $brcount);
 
 if (defined($ENV{'KBUILD_VERBOSE'}) && $ENV{'KBUILD_VERBOSE'} =~ '1') {
     $verbose = 1;
···
         $file = $orig_file;
     }
 
-    if (defined($source_map{$file})) {
-        $file = $source_map{$file};
-    }
-
     return $file;
 }
 
···
     my $result = $highlights[$k][1];
 #   print STDERR "scanning pattern:$pattern, highlight:($result)\n";
     $dohighlight .=  "\$contents =~ s:$pattern:$result:gs;\n";
-}
-
-# Read the file that maps relative names to absolute names for
-# separate source and object directories and for shadow trees.
-if (open(SOURCE_MAP, "<.tmp_filelist.txt")) {
-    my ($relname, $absname);
-    while(<SOURCE_MAP>) {
-        chop();
-        ($relname, $absname) = (split())[0..1];
-        $relname =~ s:^/+::;
-        $source_map{$relname} = $absname;
-    }
-    close(SOURCE_MAP);
 }
 
 if ($output_selection == OUTPUT_EXPORTED ||