Rework NativeInit for SPI

[josesimoes]

Description

• Reorganize code in NativeInit.
• Remove casts from calls to ComputeBaudRate.

Motivation and Context

• Resolves issues with debug session restarting for STM32 targets using SPI.
• For some reason the build in MinSizeRel (most likely optimizations) was causing issues with the code on this function.

How Has This Been Tested?

• SPI sample. Now either connected or disconnected from VS the target boots properly.

Screenshots

Types of changes

• Improvement (non-breaking change that improves a feature, code or algorithm)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

Signed-off-by: josesimoes jose.simoes@eclo.solutions

[nfbot]

Hi @josesimoes,

I'm nanoFramework bot.
Thank you for your contribution!

A human will be reviewing it shortly. 😉

[josesimoes]

ping @KiwiBryn