Fix init_cfg in resnet backbone (#697)

Author: puhsu

Diff for: mmseg/models/backbones/resnet.py

@@ -400,7 +400,7 @@ def __init__(self,
                  zero_init_residual=True,
                  pretrained=None,
                  init_cfg=None):
-        super(ResNet, self).__init__()
+        super(ResNet, self).__init__(init_cfg)
         if depth not in self.arch_settings:
             raise KeyError(f'invalid depth {depth} for resnet')