checkpatch: improve SPDX license checking

Use perl's m@<match>@ match and not /<match>/ comparisons to avoid
an error using c90's // comment style.

Miscellanea:

o Use normal tab indentation and alignment

Link: http://lkml.kernel.org/r/5e4a8fa7901148fbcd77ab391e6dd0e6bf95777f.camel@perches.com

Link: http://lkml.kernel.org/r/f08eb62458407a145cfedf959d1091af151cd665.1563575364.git.joe@perches.comSigned-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -3071,13 +3071,13 @@ sub process {
 # check SPDX comment style for .[chsS] files
 				if ($realfile =~ /\.[chsS]$/ &&
 				    $rawline =~ /SPDX-License-Identifier:/ &&
-				    $rawline !~ /^\+\s*\Q$comment\E\s*/) {
+				    $rawline !~ m@^\+\s*\Q$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: /) {
+				    $rawline !~ m@^\+\Q$comment\E SPDX-License-Identifier: @) {
 					WARN("SPDX_LICENSE_TAG",
 					     "Missing or malformed SPDX-License-Identifier tag in line $checklicenseline\n" . $herecurr);
 				} elsif ($rawline =~ /(SPDX-License-Identifier: .*)/) {