crypto: ixp4xx - Add missing npe_c release in error branches

Most error branches following the call to npe_request contain a call to
npe_request. This patch add a call to npe_release to error branches
following the call to npe_request that do not have it.

This issue was found with Hector.

Signed-off-by: Quentin Lambert <lambert.quentin@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>