drm/amd/display: p-state warning occurs while changing resolution from 120hz to 60hz

drm/amd/display: p-state warning occurs while changing resolution from 120hz to 60hz

[Why]
new calculated dispclk, dppclk are stored in
context->bw_ctx.bw.dcn.clk.dispclk_khz, dppclk_khz. Current dispclk,
dppclk are from dc->clk_mgr->clks.dispclk_khz. dcn_validate_bandwidth
compute new dispclk, dppclk. dispclk will put in use after
optimize_bandwidth when ramp_up_dispclk_with_dpp is called. There are
two places for dppclk be put in use. One location is the same as the
location as dispclk. Another is within update_dchubp_dpp which happens
between pre_bandwidth and optimize_bandwidth. dppclk updated within
update_dchubp_dpp will cause new clock values of dispclk and dppclk not
be in use at the same time. when clocks are decreased, this may cause
dppclk is lower than current configuration and let pipe stuck. for
example, eDP + external dp, change resolution of DP from 1920x1080x144hz
to 1280x960x60hz.

before change: dispclk = 337889 dppclk = 337889
change mode, dcn_validate_bandwidth calculate
             dispclk = 143122 dppclk = 143122
update_dchubp_dpp be executed before dispclk be updated,
dispclk = 337889, but dppclk use new value dispclk /2 =
168944. this will cause pipe pstate warning issue.

[How]
between pre_bandwidth and optimize_bandwidth, while dispclk is going to
be decreased, keep dppclk = dispclk

Signed-off-by: Hersen Wu <hersenxs.wu@amd.com>
Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>