checkpatch: improve quoted string and line continuation test

Given this patch context,

+#define EFI_ST_DISK_IMG { \
+       0x00000240, "\xbe\x5b\x7c\xac\x22\xc0\x74\x0b" /* .[|.".t. */ \
+       }

the current code misreports a quoted string line continuation defect as
there is a single quote in comment.

The 'raw' line should not be tested for quote count, the comment
substituted line should be instead.

Link: http://lkml.kernel.org/r/13f2735df10c33ca846e26f42f5cce6618157200.1513698599.git.joe@perches.com
Signed-off-by: Joe Perches <joe@perches.com>
Reported-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -5312,7 +5312,7 @@ sub process {
 		}
 
 # check for line continuations in quoted strings with odd counts of "
-		if ($rawline =~ /\\$/ && $rawline =~ tr/"/"/ % 2) {
+		if ($rawline =~ /\\$/ && $sline =~ tr/"/"/ % 2) {
 			WARN("LINE_CONTINUATIONS",
 			     "Avoid line continuations in quoted strings\n" . $herecurr);
 		}