drm/amd/display: Disable dsc_power_gate for dcn314 by default

[Why]
"REG_WAIT timeout 1us * 1000 tries - dcn314_dsc_pg_control line"
warnings seen after resuming from s2idle.
DCN314 has issues with DSC power gating that cause REG_WAIT timeouts
when attempting to power down DSC blocks.

[How]
Disable dsc_power_gate for dcn314 by default.

Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Roman Li <Roman.Li@amd.com>
Signed-off-by: Ivan Lipski <ivan.lipski@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>