get_maintainer: fix unexpected behavior for path/to//file (double slashes)

get_maintainer behaves differently if there is a double sequential forward
slash in a filename because the total number of slashes in a filename is
used to match MAINTAINERS file patterns.

For example:

(with double slash)
  $ ./scripts/get_maintainer.pl -f drivers/gpu/drm//lima
  David Airlie <airlied@linux.ie> (maintainer:DRM DRIVERS)
  Daniel Vetter <daniel@ffwll.ch> (maintainer:DRM DRIVERS,commit_signer:3/42=7%)
  Qiang Yu <yuq825@gmail.com> (commit_signer:36/42=86%,authored:24/42=57%)
  Vasily Khoruzhick <anarsoul@gmail.com> (commit_signer:26/42=62%)
  Krzysztof Kozlowski <krzk@kernel.org> (commit_signer:5/42=12%,authored:5/42=12%)
  Emil Velikov <emil.velikov@collabora.com> (commit_signer:4/42=10%)
  dri-devel@lists.freedesktop.org (open list:DRM DRIVERS)
  linux-kernel@vger.kernel.org (open list)

(without double slash)
  $ ./scripts/get_maintainer.pl -f drivers/gpu/drm/lima
  Qiang Yu <yuq825@gmail.com> (maintainer:DRM DRIVERS FOR LIMA)
  David Airlie <airlied@linux.ie> (maintainer:DRM DRIVERS)
  Daniel Vetter <daniel@ffwll.ch> (maintainer:DRM DRIVERS)
  dri-devel@lists.freedesktop.org (open list:DRM DRIVERS FOR LIMA)
  lima@lists.freedesktop.org (moderated list:DRM DRIVERS FOR LIMA)
  linux-kernel@vger.kernel.org (open list)

So reduce consecutive double slashes to a single slash
by using File::Spec->canonpath().

from: https://perldoc.perl.org/File/Spec/Unix.html

canonpath()

No physical check on the filesystem, but a logical cleanup of a path.  On
UNIX eliminates successive slashes and successive "/.".
Reported-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/9a18b611813bb409fef15bc8927adab79eb9be43.camel@perches.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/get_maintainer.pl

@@ -19,6 +19,7 @@ my $V = '0.26';
 use Getopt::Long qw(:config no_auto_abbrev);
 use Cwd;
 use File::Find;
+use File::Spec::Functions;
 
 my $cur_path = fastgetcwd() . '/';
 my $lk_path = "./";
@@ -532,6 +533,7 @@ if (!@ARGV) {
 
 foreach my $file (@ARGV) {
     if ($file ne "&STDIN") {
+	$file = canonpath($file);
 	##if $file is a directory and it lacks a trailing slash, add one
 	if ((-d $file)) {
 	    $file =~ s@([^/])$@$1/@;