Implement abstraction layer for the SPI modules

[lucas-yotsui]

Tasks

For this issue to be considered completed, the following tasks must be fulfilled:

Implementation

• Map all the registers related to the SPI modules.
• Implement functions for abstracting register access.
  NOTE: Investigate how to use the DMA module for sending or receiving data through this interface and if it is worth the effort.

Documentation

• Document the role of each register.
• Document the role of each bit on each register.
• Document how to use all the functions.

Testing

• Write unit tests for all that can be tested in such a way
• Test the rest of the functionality manually and ensure everything works properly.