crypto: omap-sham - fix memleak

Fixes: 8043bb1a ("crypto: omap-sham - convert driver logic to use sgs for data xmit")

The memory pages freed in omap_sham_finish_req() were less than those
allocated in omap_sham_copy_sgs().

Cc: stable@vger.kernel.org
Signed-off-by: Bin Liu <b-liu@ti.com>
Acked-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>