checkpatch: get default codespell dictionary path from package location

The standard location of dictionary.txt is under codespell's package, on
my machine atm (codespell 2.1, Artix Linux):
/usr/lib/python3.9/site-packages/codespell_lib/data/dictionary.txt

Since we enable the codespell by default for SOF I have constant:
No codespell typos will be found - \
file '/usr/share/codespell/dictionary.txt': No such file or directory

The patch proposes to try to fix up the path following the recommendation
found here:
codespell-project/codespell#1540

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>

scripts/checkpatch.pl

@@ -63,6 +63,7 @@
 my $spelling_file = "$D/spelling.txt";
 my $codespell = 0;
 my $codespellfile = "/usr/share/codespell/dictionary.txt";
+my $user_codespellfile = "";
 my $conststructsfile = "$D/const_structs.checkpatch";
 my $docsfile = "$D/../Documentation/dev-tools/checkpatch.rst";
 my $typedefsfile;
@@ -130,7 +131,7 @@ sub help {
   --ignore-perl-version      override checking of perl version.  expect
                              runtime errors.
   --codespell                Use the codespell dictionary for spelling/typos
-                             (default:/usr/share/codespell/dictionary.txt)
+                             (default:$codespellfile)
   --codespellfile            Use this codespell dictionary
   --typedefsfile             Read additional types from this file
   --color[=WHEN]             Use colors 'always', 'never', or only when output
@@ -317,17 +318,30 @@ sub load_docs {
 	'debug=s'	=> \%debug,
 	'test-only=s'	=> \$tst_only,
 	'codespell!'	=> \$codespell,
-	'codespellfile=s'	=> \$codespellfile,
+	'codespellfile=s'	=> \$user_codespellfile,
 	'typedefsfile=s'	=> \$typedefsfile,
 	'color=s'	=> \$color,
 	'no-color'	=> \$color,	#keep old behaviors of -nocolor
 	'nocolor'	=> \$color,	#keep old behaviors of -nocolor
 	'kconfig-prefix=s'	=> \${CONFIG_},
 	'h|help'	=> \$help,
 	'version'	=> \$help
-) or help(1);
+) or $help = 2;
 
-help(0) if ($help);
+if ($user_codespellfile) {
+	# Use the user provided codespell file unconditionally
+	$codespellfile = $user_codespellfile;
+} else {
+	# Try to find the codespell install location to use it as default path
+	if (($codespell || $help) && which("codespell") ne "" && which("python") ne "") {
+		my $codespell_dict = `python -c "import os.path as op; import codespell_lib; print(op.join(op.dirname(codespell_lib.__file__), 'data', 'dictionary.txt'), end='')" 2> /dev/null`;
+		$codespellfile = $codespell_dict if (-e $codespell_dict);
+	}
+}
+
+# $help is 1 if either -h, --help or --version is passed as option - exitcode: 0
+# $help is 2 if invalid option is passed - exitcode: 1
+help($help - 1) if ($help);
 
 die "$P: --git cannot be used with --file or --fix\n" if ($git && ($file || $fix));
 die "$P: --verbose cannot be used with --terse\n" if ($verbose && $terse);