mcp472x: Initial Add

[gsexton]

Adds support for MCP4725/MCP4728 D/A converters

Implements #85

[codecov]

Codecov Report

Attention: Patch coverage is 81.90955% with 36 lines in your changes missing coverage. Please review.

Project coverage is 52.6%. Comparing base (f009056) to head (11994ba).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
mcp472x/mcp472x.go	81.9%	26 Missing and 10 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #108     +/-   ##
=======================================
+ Coverage   52.4%   52.6%   +0.2%     
=======================================
  Files        113     114      +1     
  Lines      14226   14477    +251     
=======================================
+ Hits        7455    7620    +165     
- Misses      6425    6501     +76     
- Partials     346     356     +10     

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[maruel]

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