Add mop pattern quirk to Viomi V7

[ZephireNZ]

Type of change

Type A:

• Bug fix (non-breaking change which fixes an issue)
• UI Feature
• Refactor/Code Cleanup
• Docs
• Capability implementation for existing core capability
• New robot implementation

Type B:

• New capability
• New core feature

Description (Type A)

Viomi V7 supports the Y-pattern mopping. This simply add the existing quirk to the device type. See below:

$ miiocli device --ip <snip> --token <snip> info
Model: viomi.vacuum.v7
Hardware version: Linux
Firmware version: 3.5.3_0047

$ mirobo --ip <snip> --token <snip> raw-command get_prop '["mop_route"]'
Sending cmd get_prop with params ['mop_route']
WARNING:miio.device:Found an unsupported model 'viomi.vacuum.v7' for class 'RoborockVacuum'. If this is working for you, please open an issue at https://github.com/rytilahti/python-miio/
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