crypto: ccp - Replace dma_pool_alloc + memset with dma_pool_zalloc

Use dma_pool_zalloc instead of using dma_pool_alloc to allocate
memory and then zeroing it with memset 0.
This simplifies the code.

Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
Acked-by: Gary R Hook <gary.hook@amd.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>