selftests: hw-net: toeplitz: give the test up to 4 seconds

selftests: hw-net: toeplitz: give the test up to 4 seconds

Increase the receiver timeout. When running between machines
in different geographic regions the test needs more than
a second to SSH across and send the frames.

The bkg() command that runs the receiver defaults to 5 sec timeout,
so using 4 sec sounds like a reasonable value for the receiver itself.

Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20251121040259.3647749-6-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>