crypto: ixp4xx - Fix the size used in a 'dma_free_coherent()' call

Update the size used in 'dma_free_coherent()' in order to match the one
used in the corresponding 'dma_alloc_coherent()', in 'setup_crypt_desc()'.

Fixes: 81bef015

 ("crypto: ixp4xx - Hardware crypto support for IXP4xx CPUs")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>