tests: skip the cpu_idle test for nsim_hs_smp

Because the sleep instruction issue for nsim_hs_smp, idle
loop is used to simulate behavior of sleep, so arch_cpu_idle will
forever loop. This causes cpu idle test loop, then the whole
context test timeouts.

as a fix, skip the cpu_idle test for nsim_hs_smp now.

Signed-off-by: Wayne Ren <wei.ren@synopsys.com>