drm/amd/display: Do 1-to-1 mapping between OPP and DSC in DML2

[why]
To determine which block instance to power-gate,
we look at the available pipe resource for both plane
and stream. On MPO, DSC3 was falsely powered on even
though only 1 stream path was enabled because
the resource mapping was not done correctly.

[how]
Acquire the correct DSC instance to power on / off based
on the instance of OPP which determines the backend
pipe index.
Reviewed-by: Swapnil Patel <swapnil.patel@amd.com>
Signed-off-by: Jerry Zuo <jerry.zuo@amd.com>
Signed-off-by: Sung Joon Kim <sungjoon.kim@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc_resource.c

@@ -5166,7 +5166,7 @@ bool dc_resource_acquire_secondary_pipe_for_mpc_odm_legacy(
 			sec_pipe->stream_res.opp = sec_pipe->top_pipe->stream_res.opp;
 		if (sec_pipe->stream->timing.flags.DSC == 1) {
 #if defined(CONFIG_DRM_AMD_DC_FP)
-			dcn20_acquire_dsc(dc, &state->res_ctx, &sec_pipe->stream_res.dsc, pipe_idx);
+			dcn20_acquire_dsc(dc, &state->res_ctx, &sec_pipe->stream_res.dsc, sec_pipe->stream_res.opp->inst);
 #endif
 			ASSERT(sec_pipe->stream_res.dsc);
 			if (sec_pipe->stream_res.dsc == NULL)