checkpatch: add [] to type extensions

Add [] to a type extensions.  Fixes false positives on:

    .attrs = (struct attribute *[]) {

Signed-off-by: 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>