Replace max_data_zero_instr_stall plusarg with rand_stall_obi_disable

Replace max_data_zero_instr_stall plusarg (used in the now deprecated mm_ram.sv) with rand_stall_obi_disable supported by the new obi_memory_agent (see uvma_obi_memory_cfg.sv).

The obi_memory_agent does not have a max_data_zero_instr_stall plusarg, and without some tight constraints on the instruction fetch OBI bus the perf_counters_instructions directed test will not accurately predict performance counter values. This change also constrains the data load/store OBI bus, so we may wish to implement a max_data_zero_instr_stall type constraint in the future.

Signed-off-by: MikeOpenHWGroup mike@openhwgroup.org