arc: nsim_hs_smp: use the default value of mdb instrs_per_pass option

Instrs_per_pass option specify the number of instructions excuted
before simulator switches operations. the default value is 512. If we
specify a small value for it the debugger's overhead will increase
significantly for simulation because of the time taken to rapidly
switch operations. And the overhead will cause some time critical
task failure.

Restore instrs_per_pass value from 10 to default 512, we will have a
good sanitycheck result for nsim_hs_smp.

Signed-off-by: Watson Zeng <zhiwei@synopsys.com>