hash: fix maybe-uninitialized warnings on build

Following recent changes to the test-meson-build.sh script[1] to use more
build-types warnings are seen in the hash library GFNI code about values
possibly being uninitialized.

In function ‘_mm512_mask_permutexvar_epi8’,
    inlined from ‘__rte_thash_gfni’ at ../lib/hash/rte_thash_x86_gfni.h:150:6:
/usr/lib/gcc/x86_64-linux-gnu/15/include/avx512vbmiintrin.h:97:20:
error: ‘tuple_bytes_2’ may be used uninitialized [-Werror=maybe-uninitialized]

These all appear to be a false positive, but fix these by explicitly
zero-initializing the offending values.

[1] 177acaf ("devtools: test different build types")

Fixes: 4fd8c4c ("hash: add new Toeplitz hash implementation")
Cc: stable@dpdk.org

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Vladimir Medvedkin <vladimir.medvedkin@intel.com>
Acked-by: David Marchand <david.marchand@redhat.com>

Author: bruce-richardson

lib/hash/rte_thash_x86_gfni.h

@@ -89,9 +89,9 @@ __rte_thash_gfni(const uint64_t *mtrx, const uint8_t *tuple,
 	const __m512i shift_8 = _mm512_set1_epi8(8);
 	__m512i xor_acc = _mm512_setzero_si512();
 	__m512i perm_bytes = _mm512_setzero_si512();
-	__m512i vals, matrixes, tuple_bytes_2;
+	__m512i vals, matrixes, tuple_bytes_2 = _mm512_setzero_si512();
 	__m512i tuple_bytes = _mm512_setzero_si512();
-	__mmask64 load_mask, permute_mask_2;
+	__mmask64 load_mask, permute_mask_2 = 0;
 	__mmask64 permute_mask = 0;
 	int chunk_len = 0, i = 0;
 	uint8_t mtrx_msk;