drm/amd/display: Remove redundant condition with DEADCODE

[WHY]
Coverity analysis flagged this condition as DEADCODE since the
variable 'req128_c' is always false, thus the condition is never
true.

[HOW]
Remove the condition.
Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Acked-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Ivan Lipski <ivlipski@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dml/dcn21/display_rq_dlg_calc_21.c

@@ -297,9 +297,6 @@ static void handle_det_buf_split(
 
 		if (swath_height_c > 0)
 			log2_swath_height_c = dml_log2(swath_height_c);
-
-		if (req128_c && log2_swath_height_c > 0)
-			log2_swath_height_c -= 1;
 	}
 
 	rq_param->dlg.rq_l.swath_height = 1 << log2_swath_height_l;