crypto: qat - unmap buffer before free for DH

The callback function for DH frees the memory allocated for the
destination buffer before unmapping it.
This sequence is wrong.

Change the cleanup sequence to unmap the buffer before freeing it.

Fixes: 029aa462

 ("crypto: qat - remove dma_free_coherent() for DH")
Signed-off-by: Hareshx Sankar Raj <hareshx.sankar.raj@intel.com>
Co-developed-by: Bolemx Sivanagaleela <bolemx.sivanagaleela@intel.com>
Signed-off-by: Bolemx Sivanagaleela <bolemx.sivanagaleela@intel.com>
Reviewed-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>