drm/amd/display: Fix Vega10 lightup on S3 resume

drm/amd/display: Fix Vega10 lightup on S3 resume

[Why]
There have been a few reports of Vega10 display remaining blank
after S3 resume. The regression is caused by workaround for mode
change on Vega10 - skip set_bandwidth if stream count is 0.
As a result we skipped dispclk reset on suspend, thus on resume
we may skip the clock update assuming it hasn't been changed.
On some systems it causes display blank or 'out of range'.

[How]
Revert "drm/amd/display: Fix Vega10 black screen after mode change"
Verified that it hadn't cause mode change regression.

Signed-off-by: Roman Li <Roman.Li@amd.com>
Reviewed-by: Sun peng Li <Sunpeng.Li@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>