drm/msm/dpu: Fix error return code in dpu_mdss_init()

The error code returned by platform_get_irq() is stored in 'irq', it's
forgotten to be copied to 'ret' before being returned. As a result, the
value 0 of 'ret' is returned incorrectly.

After the above fix is completed, initializing the local variable 'ret'
to 0 is no longer needed, remove it.

In addition, when dpu_mdss_init() is successfully returned, the value of
'ret' is always 0. Therefore, replace "return ret" with "return 0" to make
the code clearer.

Fixes: 070e64dc ("drm/msm/dpu: Convert to a chained irq chip")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Link: https://lore.kernel.org/r/20210510063805.3262-2-thunder.leizhen@huawei.comReviewed-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/disp/dpu1/dpu_mdss.c

@@ -225,7 +225,7 @@ int dpu_mdss_init(struct drm_device *dev)
 	struct msm_drm_private *priv = dev->dev_private;
 	struct dpu_mdss *dpu_mdss;
 	struct dss_module_power *mp;
-	int ret = 0;
+	int ret;
 	int irq;
 
 	dpu_mdss = devm_kzalloc(dev->dev, sizeof(*dpu_mdss), GFP_KERNEL);
@@ -253,8 +253,10 @@ int dpu_mdss_init(struct drm_device *dev)
 		goto irq_domain_error;
 
 	irq = platform_get_irq(pdev, 0);
-	if (irq < 0)
+	if (irq < 0) {
+		ret = irq;
 		goto irq_error;
+	}
 
 	irq_set_chained_handler_and_data(irq, dpu_mdss_irq,
 					 dpu_mdss);
@@ -263,7 +265,7 @@ int dpu_mdss_init(struct drm_device *dev)
 
 	pm_runtime_enable(dev->dev);
 
-	return ret;
+	return 0;
 
 irq_error:
 	_dpu_mdss_irq_domain_fini(dpu_mdss);