Update CMakeLists.txt to include "Adafruit_GenericDevice.cpp"

[mak0t0san]

Missing source file "Adafruit_GenericDevice.cpp"

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Issue
When using Adafruit_BusIO as a component in an ESP32 project that uses CMake for the build, the compilation will fail with this error:

Adafruit_BusIO_Register.cpp:245:(.text._ZN23Adafruit_BusIO_Register4readEPhh+0xaa): undefined reference to `Adafruit_GenericDevice::readRegister(unsigned char*, unsigned char, unsigned char*, unsigned short)'

Resolution
Add the missing reference to the source file 'Adafruit_GenericDevice.cpp' to CMakesLists.txt

Testing
Tested on a Windows 11 PC with Espressif IDE (inside of Visual Studio Code). Ran idf.py build
Error prior to change, successful build after the change