selftests: ncdevmem: remove sleep on rx

selftests: ncdevmem: remove sleep on rx

RX devmem sometimes fails on NIPA:

https://netdev-3.bots.linux.dev/vmksft-fbnic-qemu-dbg/results/294402/7-devmem-py/

Both RSS and flow steering are properly installed, but the wait_port_listen
fails. Try to remove sleep(1) to see if the cause of the failure is
spending too much time during RX setup. I don't see a good reason to
have sleep in the first place. If there needs to be a delay between
installing the rules and receiving the traffic, let's add it to the
callers (devmem.py) instead.

Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
Reviewed-by: Mina Almasry <almasrymina@google.com>
Link: https://patch.msgid.link/20250912170611.676110-1-sdf@fomichev.me
Signed-off-by: Jakub Kicinski <kuba@kernel.org>