crypto: qat - extend buffer list interface

The compression service requires an additional pre-allocated buffer for
each destination scatter list.
Extend the function qat_alg_sgl_to_bufl() to take an additional
structure that contains the dma address and the size of the extra
buffer which will be appended in the destination FW SGL.

The logic that unmaps buffers in qat_alg_free_bufl() has been changed to
start unmapping from buffer 0 instead of skipping the initial buffers
num_buff - num_mapped_bufs as that functionality was not used in the
code.

Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Reviewed-by: Wojciech Ziemba <wojciech.ziemba@intel.com>
Reviewed-by: Adam Guerin <adam.guerin@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>