drm/amd/display: fix a divided-by-zero error

[Why & How]

timing.dsc_cfg.num_slices_v can be zero and it is necessary to check
before using it.

This fixes the error "divide error: 0000 [#1] PREEMPT SMP NOPTI".
Reviewed-by: Aurabindo Pillai <Aurabindo.Pillai@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/modules/power/power_helpers.c

@@ -927,6 +927,10 @@ bool psr_su_set_dsc_slice_height(struct dc *dc, struct dc_link *link,
 
 	pic_height = stream->timing.v_addressable +
 		stream->timing.v_border_top + stream->timing.v_border_bottom;
+
+	if (stream->timing.dsc_cfg.num_slices_v == 0)
+		return false;
+
 	slice_height = pic_height / stream->timing.dsc_cfg.num_slices_v;
 	config->dsc_slice_height = slice_height;