cocci: extend WRITE_ONCE detection for const script

It was suggesting that ctx should be marked const:

  static __always_inline __maybe_unused void
  bpf_clear_meta(struct __sk_buff *ctx)
  {
        __u32 zero = 0;

        WRITE_ONCE(ctx->cb[0], zero);
        WRITE_ONCE(ctx->cb[1], zero);
        WRITE_ONCE(ctx->cb[2], zero);
        WRITE_ONCE(ctx->cb[3], zero);
        WRITE_ONCE(ctx->cb[4], zero);
  }

Extend to cover x->z[...].

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

contrib/coccinelle/const.cocci

@@ -43,6 +43,7 @@ position p;
       when != &x->z
       when != e = x
       when != WRITE_ONCE(x->z, ...)
+      when != WRITE_ONCE(x->z[...], ...)
       when != f(..., x, ...)
       // Special case for the addr field since it's an array in several
       // structures.