crypto: ixp4xx - Remove bogus BUG_ON on scattered dst buffer

commit f898c522f0e9ac9f3177d0762b76e2ab2d2cf9c0 upstream.

This patch removes a bogus BUG_ON in the ablkcipher path that
triggers when the destination buffer is different from the source
buffer and is scattered.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>