drm/amd/display: Remove set but not used variable 'pixel_width'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/gpu/drm/amd/display/dc/dcn20/dcn20_dpp.c: In function dpp2_get_optimal_number_of_taps:
drivers/gpu/drm/amd/display/dc/dcn20/dcn20_dpp.c:359:11: warning: variable pixel_width set but not used [-Wunused-but-set-variable]

It is not used since commit f7de96ee ("drm/amd/display:
Add DCN2 DPP")
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn20/dcn20_dpp.c

@@ -376,13 +376,6 @@ bool dpp2_get_optimal_number_of_taps(
 		struct scaler_data *scl_data,
 		const struct scaling_taps *in_taps)
 {
-	uint32_t pixel_width;
-
-	if (scl_data->viewport.width > scl_data->recout.width)
-		pixel_width = scl_data->recout.width;
-	else
-		pixel_width = scl_data->viewport.width;
-
 	/* Some ASICs does not support  FP16 scaling, so we reject modes require this*/
 	if (scl_data->viewport.width  != scl_data->h_active &&
 		scl_data->viewport.height != scl_data->v_active &&