Issue detected by coverity. Could never actually cause a
problem as truncated value (0x7f7f7f7f->0x7f) is what's needed.
But fix in code for correctness.
Coverity issue: 194998
Fixes: 571365dd4c ("crypto/qat: enable Rx head writes coalescing")
Cc: stable@dpdk.org
Signed-off-by: Fiona Trahe <fiona.trahe@intel.com>