[New Configs] Add new config file for MobileNetV3 and cityscapes in mmseg/configs folder

[tackhwa]

• The Configs file had been tested, all the training can be run properly and the inference result is same as result in this link

• Training for mobilenet_v3_d8_s_lraspp_4xb4-320k_cityscapes_512x1024.py

• Training for mobilenet_v3_d8_scratch_lraspp_4xb4_320k_cityscapes_512x1024.py

• Training for mobilenet_v3_d8_scratch_s_lraspp_4xb4_320k_cityscapes_512x1024.py

• Training for mobilenet_v3_d8_lraspp_4xb4_320k_cityscapes_512x1024.py

• Inference result of mobilenet_v3/mobilenet-v3-d8_lraspp_4xb4-320k_cityscapes-512x1024.py

• Inference result of mobilenet_v3_d8_s_lraspp_4xb4_320k_cityscapes_512x1024.py

• Inference result of mobilenet_v3_d8_scratch_lraspp_4xb4_320k_cityscapes_512x1024.py

• Inference result of mobilenet_v3_d8_scratch_s_lraspp_4xb4_320k_cityscapes_512x1024.py