crypto: nx - fix physical addresses added to sg lists

The co-processor receives data to be hashed through scatter/gather lists
pointing to physical addresses. When a vmalloc'ed data is given, the
driver must calculate the physical address to each page of the data.

However the current version of it just calculates the physical address
once and keeps incrementing it even when a page boundary is crossed.
This patch fixes this behaviour.

Reviewed-by: Fionnuala Gunter <fin@linux.vnet.ibm.com>
Reviewed-by: Joel Schopp <jschopp@linux.vnet.ibm.com>
Reviewed-by: Joy Latten <jmlatten@linux.vnet.ibm.com>
Signed-off-by: Marcelo Cerri <mhcerri@linux.vnet.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>