acl: fix build with gcc 5.4.0

acl: fix build with gcc 5.4.0

gcc 5.4 fails with:
../lib/librte_acl/acl_run_avx512x8.h: In function 'match_process_avx512x8':
../lib/librte_acl/acl_run_avx512x8.h:382:31: error:
pointer targets in passing argument 1 of '_mm256_mask_i32scatter_epi32'
differ in signedness [-Werror=pointer-sign]

Later gcc versions work fine, as for them parameter type was
changed to 'void *'.
Fixed by applying explicit cast for offending argument.

Bugzilla ID: 556
Fixes: b64c2295f7fc ("acl: add 256-bit AVX512 classify method")
Fixes: 45da22e42ec3 ("acl: add 512-bit AVX512 classify method")
Reported-by: Ali Alnubani <alialnu@nvidia.com>
Signed-off-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
Tested-by: Ali Alnubani <alialnu@nvidia.com>