drm/radeon/dpm: fix si_calculate_memory_refresh_rate()
drm/radeon/dpm: fix si_calculate_memory_refresh_rate()

Update alogorithm as per internal advice.

Signed-off-by: Alex Deucher <08dc22c6156113f2deff178e35e3ed9b24d6af9e@amd.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs