selftests: drv-net: rename queues check_xdp to check_xsk

The test is for AF_XDP, we refer to AF_XDP as XSK.

Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Reviewed-by: Joe Damato <jdamato@fastly.com>
Tested-by: Joe Damato <jdamato@fastly.com>
Link: https://patch.msgid.link/20250219234956.520599-8-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>