drm/amd/display: correct idle_power_optimizations disablement return value

[Why]
The return value indicates whether the operation(disable/enable) succeeded
or not. The existing logic reports wrong result even if the disablement was
performed successfully. That will make succeeding reenablement abandoned
as dc->idle_optimizations_allowed is always true.

[How]
Correct the return value to reflect the real result of disablement.

Fixes: 235c6763 ("drm/amd/display: add DCN32/321 specific files for Display Core")
Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn32/dcn32_hwseq.c

@@ -377,7 +377,7 @@ bool dcn32_apply_idle_power_optimizations(struct dc *dc, bool enable)
 	dc_dmub_srv_cmd_execute(dc->ctx->dmub_srv);
 	dc_dmub_srv_wait_idle(dc->ctx->dmub_srv);
 
-	return false;
+	return true;
 }
 
 /* Send DMCUB message with SubVP pipe info