drm/amd/pp: Fix sclk in highest two levels when compute on smu7

Compute workload tends to be "bursty", Only tune the behavior of
nature dpm don't work well for most of such workloads. From test
results, Fix sclk in highest two levels can get better performance.
so add min sclk setting into the default cumpute workload policy on
smu7.

user still can change sclk range through sysfs pp_dpm_sclk
for better perf/watt.

Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>