drm/amdgpu: decline max_me for mec2_fw remove in renoir/arcturus

The value of max_me in amdgpu_gfx_rlc_setup_cp_table should reduce to 4
when mec2_fw is removed on asic renoir/arcturus. Or it will cause kernel
NULL pointer when modprobe driver.

Signed-off-by: Changfeng <Changfeng.Zhu@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>