Fixup SPI init procedure, SPI EEPROM sequencing

[tzarc]

Description

Something weird going on with SPI in the sense that the first use would seemingly fail after init, but only on RP2040.
Under normal circumstances, the first read would be EEPROM when using SPI EEPROM, specifically the magic... which would then trigger an EEPROM reset as the data returned is zero'd out on SPI failure.

This PR changes the sequencing:

• On spi_init it stops the SPI peripheral as a final action,
• SPI EEPROM now restarts the SPI peripheral each time the status register is read
• SPI EEPROM driver is now slightly more defensive w.r.t. executing spi_stop() on failure -- the previous assumption was that spi_start() failing did not necessitate a subsequent spi_stop() -- this now explicitly invokes the stop upon all failures.

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• 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.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[KarlK90]

On spi_init it stops the SPI peripheral as a final action

As a precaution - I've checked all the places that this is called and all drivers do issue a spi_start() before doing anything (as they should) so this should not break anything. Curious why this fails on the RP2040 though. I don't have a SPI flash chip to test but otherwise this LGTM.

[drashna]

Tested with SPI eeprom chip on a blackpill, and doesn't seem to adversely effect it (this is including with other SPI devices attached too, namely the pmw3360).

[KarlK90]

Oh wow, I do have an SPI EEPROM. Somehow I read it as SPI Flash all the time. Going to test it this evening with rp2040.

[KarlK90]

Tested with rp2040 and spi eeprom, LGTM!