drm/amd/display: Clear the CUR_ENABLE register on DCN314 w/out DPP PG

drm/amd/display: Clear the CUR_ENABLE register on DCN314 w/out DPP PG

[Why&How]
ON DCN314, clearing DPP SW structure without power gating it can cause a
double cursor in full screen with non-native scaling.

A W/A that clears CURSOR0_CONTROL cursor_enable flag if
dcn10_plane_atomic_power_down is called and DPP power gating is disabled.

Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4168
Reviewed-by: Sun peng (Leo) Li <sunpeng.li@amd.com>
Signed-off-by: Ivan Lipski <ivan.lipski@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>