Consistently use AES_KEYSIZE_128 instead of arbitrary defined value.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Dmitry Kasatkin <dmitry.kasatkin@nokia.com>
Cc: Eric Bénard <eric@eukrea.com>
Cc: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Cc: Kent Yoder <key@linux.vnet.ibm.com>
Cc: Michal Ludvig <michal@logix.cz>
Cc: Varun Wadekar <vwadekar@nvidia.com>
Cc: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Cc: linux-geode@lists.infradead.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>