selftests/bpf: xdp_hw_metadata reduce sleep interval

selftests/bpf: xdp_hw_metadata reduce sleep interval

In current ping-pong design, xdp_hw_metadata will wait until the packet
transmission completely done, then only start to receive the next packet.

The current sleep interval is 10ms, which is unnecessary large. Typically,
a NIC does not need such a long time to transmit a packet. Furthermore,
during this 10ms sleep time, the app is unable to receive incoming packets.

Therefore, this commit reduce sleep interval to 10us, so that
xdp_hw_metadata is able to support periodic packets with shorter interval.
10us * 500 = 5ms should be enough for packet transmission and status
retrieval.

Signed-off-by: Song Yoong Siang <yoong.siang.song@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/20240303083225.1184165-2-yoong.siang.song@intel.com