drm/amd/display: Set compbuf size to min at prep prevent overbook crb

[Why]
Detbuffer size is dynamically set for dcn31x. At certain moment,
compbuf+(def size * num pipes) > config return buffer size causing
flickering. This is easily reproducible when MPO is
enabled with two displays.

[How]
At prepare BW, use the min comp buffer size. When it is to
optimize BW, set compbuf size back to maximum possible size.

Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Duncan Ma <duncanma@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn315/dcn315_resource.c

@@ -147,6 +147,7 @@ struct _vcs_dpi_ip_params_st dcn3_15_ip = {
 	.hostvm_max_page_table_levels = 2,
 	.rob_buffer_size_kbytes = 64,
 	.det_buffer_size_kbytes = DCN3_15_DEFAULT_DET_SIZE,
+	.min_comp_buffer_size_kbytes = DCN3_15_MIN_COMPBUF_SIZE_KB,
 	.config_return_buffer_size_in_kbytes = 1024,
 	.compressed_buffer_segment_size_in_kbytes = 64,
 	.meta_fifo_size_in_kentries = 32,