selftests: net: io_uring_zerocopy: enable io_uring for the test

selftests: net: io_uring_zerocopy: enable io_uring for the test

The io_uring_zerocopy.sh kselftest assumes that io_uring support is
enabled on the host system. When io_uring is disabled via the
kernel.io_uring_disabled sysctl, the test fails.

Explicitly enable io_uring for the test by setting
kernel.io_uring_disabled=0.

Save the original value of kernel.io_uring_disabled before changing
it and restore it in cleanup handler to ensure the system state is
restored regardless of test outcome.

Signed-off-by: Aleksei Oladko <aleksey.oladko@virtuozzo.com>
Signed-off-by: Konstantin Khorenko <khorenko@virtuozzo.com>
Link: https://patch.msgid.link/20260321215908.175465-5-aleksey.oladko@virtuozzo.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>