checkpatch: add Suggested-by as a standard signature

As people started using Suggested-by as standard signature, adding
"Suggested-by" to the standard signature so that checkpatch won't
generate warning when Suggested-by is used in patch signature

Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: 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

@@ -281,6 +281,7 @@ our $signature_tags = qr{(?xi:
 	Tested-by:|
 	Reviewed-by:|
 	Reported-by:|
+	Suggested-by:|
 	To:|
 	Cc:
 )};