Remove hardcoded model information from mdns discovery

[rytilahti]

As the mdns name can be converted into a model name, there is no need to hardcode any of this information.

[codecov-commenter]

Codecov Report

Merging #1695 (30cc18f) into master (131a555) will decrease coverage by 0.44%.
The diff coverage is 25.00%.

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@@            Coverage Diff             @@
##           master    #1695      +/-   ##
==========================================
- Coverage   80.04%   79.60%   -0.44%     
==========================================
  Files         161      161              
  Lines       16163    16149      -14     
  Branches     3645     3641       -4     
==========================================
- Hits        12937    12855      -82     
- Misses       2963     3015      +52     
- Partials      263      279      +16     

Impacted Files	Coverage Δ
miio/devtools/simulators/miotsimulator.py	0.00% <0.00%> (ø)
miio/discovery.py	34.88% <20.83%> (-13.77%)	⬇️
miio/miot_models.py	63.63% <100.00%> (+0.64%)	⬆️
miio/alarmclock.py	0.00% <0.00%> (-69.15%)	⬇️

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