checkpatch: verify SPDX comment style

Using SPDX commenting style // or /* is specified for various file types
in Documentation/process/license-rules.rst so add an appropriate test for
.[chsS] files because many proposed file additions and patches do not use
the correct style.

Link: http://lkml.kernel.org/r/8b02899853247a2c67669561761f354dd3bd110e.camel@perches.comSigned-off-by: Joe Perches <joe@perches.com>
Cc: Rob Herring <robh@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -3037,6 +3037,14 @@ sub process {
 					$comment = '..';
 				}
 
+# check SPDX comment style for .[chsS] files
+				if ($realfile =~ /\.[chsS]$/ &&
+				    $rawline =~ /SPDX-License-Identifier:/ &&
+				    $rawline !~ /^\+\s*\Q$comment\E\s*/) {
+					WARN("SPDX_LICENSE_TAG",
+					     "Improper SPDX comment style for '$realfile', please use '$comment' instead\n" . $herecurr);
+				}
+
 				if ($comment !~ /^$/ &&
 				    $rawline !~ /^\+\Q$comment\E SPDX-License-Identifier: /) {
 					 WARN("SPDX_LICENSE_TAG",