drm/msm/dpu: use defined symbol for sc8280xp's maxwidth

Use defined name DEFAULT_DPU_OUTPUT_LINE_WIDTH instead of open coding
the value.
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/530866/
Link: https://lore.kernel.org/r/20230404130622.509628-30-dmitry.baryshkov@linaro.orgSigned-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

drivers/gpu/drm/msm/disp/dpu1/catalog/dpu_8_0_sc8280xp.h

@@ -8,7 +8,7 @@
 #define _DPU_8_0_SC8280XP_H
 
 static const struct dpu_caps sc8280xp_dpu_caps = {
-	.max_mixer_width = 2560,
+	.max_mixer_width = DEFAULT_DPU_OUTPUT_LINE_WIDTH,
 	.max_mixer_blendstages = 11,
 	.qseed_type = DPU_SSPP_SCALER_QSEED4,
 	.has_src_split = true,