harness: Make RISC-V use SYS_eventfd2 instead of unavailable SYS_eventfd
This is a recent architecture and as such does not provide legacy
support for SYS_eventfd. Declare that we need to use the new syscall.
Signed-off-by: Guillem Jover <guillem@hadrons.org>
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>