drm/amd/display: Require minimum VBlank size for stutter optimization

drm/amd/display: Require minimum VBlank size for stutter optimization

If the nominal VBlank is too small, optimizing for stutter can cause
the prefetch bandwidth to increase drasticaly, resulting in higher
clock and power requirements. Only optimize if it is >3x the stutter
latency.

Reviewed-by: Austin Zheng <austin.zheng@amd.com>
Signed-off-by: Dillon Varone <dillon.varone@amd.com>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 003215f962cdf2265f126a3f4c9ad20917f87fca)
Cc: stable@vger.kernel.org