Add missing break statement in order to prevent the code from falling
through to case S_DIN_to_DES.

This bug was found thanks to the ongoing efforts to enable
-Wimplicit-fallthrough.

Fixes: 63ee04c8 ("crypto: ccree - add skcipher support")
Cc: stable@vger.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>