scripts/checkpatch.pl: add warnings for static char that could be static const char

Add warnings for possible missing const uses of
	static char foo[] = "bar"
    that could be
	static const char foo[] = "bar"
and
	static const char *foo[] = {"bar", "baz"}
    that could be
	static const char * const foo[] = {"bar", "baz"}

Signed-off-by: Joe Perches <joe@perches.com>
Cc: Mike Frysinger <vapier.adi@gmail.com>
Cc: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>