selftests/bpf: Fix xdp_synproxy compilation failure in 32-bit arch

xdp_synproxy fails to be compiled in the 32-bit arch, log is as follows:

  xdp_synproxy.c: In function 'parse_options':
  xdp_synproxy.c:175:36: error: left shift count >= width of type [-Werror=shift-count-overflow]
    175 |                 *tcpipopts = (mss6 << 32) | (ttl << 24) | (wscale << 16) | mss4;
        |                                    ^~
  xdp_synproxy.c: In function 'syncookie_open_bpf_maps':
  xdp_synproxy.c:289:28: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
    289 |                 .map_ids = (__u64)map_ids,
        |                            ^

Fix it.

Fixes: fb5cd0ce ("selftests/bpf: Add selftests for raw syncookie helpers")
Signed-off-by: Yang Jihong <yangjihong1@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20221111030836.37632-1-yangjihong1@huawei.com