[SYCL][test-e2e] Fix off-by-one in atomic_memory_order_seq_cst check loop (#21535)
The checked_buf is allocated with dimensions (N_items / 2 * N_iters +
1), and the inner initialization loop correctly iterates up to that
bound. However, the outer loop used N_items / 2 * N_iters as its upper
bound, leaving the last row of the checked buffer uninitialized. Fix the
outer loop bound to match the buffer size and the inner loop bound.