drm/amd/pp: Memory Latency is always 25us on Vega10

For HBM, 25us latency is enough for memory clock switch.

Acked-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>