drm/amd/display: do not override CURSOR_REQ_MODE when SubVP is not enabled

[Why]
HUBP_UNBOUNDED_REQ_MODE and CURSOR_REQ_MODE are normally set together.
In hubp32_prepare_subvp_buffering() call, CURSOR_REQ_MODE is set based on
whether SubVP is enabled or not.  For non MPO case, both REQ_MODE
registers are set to 1.  But since SubVP is not enabled, then
CURSOR_REQ_MODE is set to 0, overriding the previous value.

[How]
Do not set CURSOR_REQ_MODE to 0 if SubVP is not enabled.  This
will allow CURSOR_REQ_MODE to stay as 1 in the non MPO case.
Add note to follow up and check case for single pipe MPO and
SubVP enabled as this would cause both REQ_MODE registers to be
set to 0 but SubVP enabled would override CURSOR_REQ_MODE to 1.
Signed-off-by: Samson Tam <Samson.Tam@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -555,10 +555,13 @@ void dcn32_program_mall_pipe_config(struct dc *dc, struct dc_state *context)
 		struct hubp *hubp = pipe->plane_res.hubp;
 
 		if (pipe->stream && hubp && hubp->funcs->hubp_prepare_subvp_buffering) {
+			/* TODO - remove setting CURSOR_REQ_MODE to 0 for legacy cases
+			 *      - need to investigate single pipe MPO + SubVP case to
+			 *        see if CURSOR_REQ_MODE will be back to 1 for SubVP
+			 *        when it should be 0 for MPO
+			 */
 			if (pipe->stream->mall_stream_config.type == SUBVP_MAIN) {
 				hubp->funcs->hubp_prepare_subvp_buffering(hubp, true);
-			} else {
-				hubp->funcs->hubp_prepare_subvp_buffering(hubp, false);
 			}
 		}
 	}