Remove a warning with gcc 12.x about maybe-uninitialized
Remove a warning with gcc 12.x about maybe-uninitialized

Symptoms:

In function ‘void vst1_s32(int32_t*, int32x2_t)’,
    inlined from ‘void hwy::N_NEON::StoreU(Vec64<int>, Full64<int>, int32_t*)’ at /<<PKGBUILDDIR>>/hwy/ops/arm_neon-inl.h:2804:11,
    inlined from ‘void hwy::N_NEON::Store(Vec128<T, N>, Simd<T, kNumLanes, 0>, T*) [with T = int; unsigned int N = 2]’ at /<<PKGBUILDDIR>>/hwy/ops/arm_neon-inl.h:2891:9,
    inlined from ‘void hwy::N_NEON::TestSet::operator()(T, D) [with T = int; D = hwy::N_NEON::Simd<int, 2, 0>]’ at /<<PKGBUILDDIR>>/hwy/highway_test.cc:139:10:
/usr/lib/gcc/arm-linux-gnueabihf/12/include/arm_neon.h:10907:27: warning: ‘a’ may be used uninitialized [-Wmaybe-uninitialized]
10907 |   __builtin_neon_vst1v2si ((__builtin_neon_si *) __a, __b);
      |   ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

google/highway,google/highway,google/highway