crypto: des_s390: use generic weak key check

Get rid of the des_s390 specific key check module and use the generic DES
weak key check instead. Also use the generic DES header and remove the
weak key check in 3DES mode, as RFC2451 mentions that the DES weak keys
are not relevant for 3DES.

Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>