crypto: qat - change slice->regions to slice->region

Change ptr name slice->regions to slice->region to reflect the same
in the page struct.

Signed-off-by: Pingchao Yang <pingchao.yang@intel.com>
Signed-off-by: Tadeusz Struk <tadeusz.struk@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>