drm/amd/display: correct register Clock Gater incorrectly disabled

[why]
The "dpp35_dppclk_control" routine is incorrectly disabling the register clock gater
when the DPP is enabled.

The "DISPCLK_R_GATE_DISABLE" should never be set to 1 in the normal operating mode.
This will disable the clock gater and the DPPCLK register clock branch will always be running.
As a consequence, the dynamic power will be higher than expected.

Reviewed-by: Alvin Lee <alvin.lee2@amd.com>
Signed-off-by: Charlene Liu <Charlene.Liu@amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>