Add support for SPI

[ABIbreak]

This PR will add support for SPI to sddf in terms of the following deliverables:

1. Driver for the OpenTitan SPI host device with PULP patches
2. Virtualiser for SPI
3. Client for a SPI flash

[ABIbreak]

Blocking on:

• Diagnose difference in behavior when enabling CSAAT
• Extend recieve_data to support slices at arbitrary alignments
• Write client for SPI flash
• Create libspi, mirroring libi2c
• Add support for SPI configuration (CPHA, CPOL, clock frequency) in the config struct

[ABIbreak]

Nice-to-haves:

• Add Javadoc comments for functions
• Add licenses to files
• Run clang format
• Do outstanding TODOs that still exist in the code
• Update examples/spi/{Makefile, build.zig, build.zig.zon}
• Write documentation

[ABIbreak]

In the driver, config.slice_size is set manually; I will update sdfgen to populate this automatically

EDIT: done

[Ivan-Velickovic]

@ABIbreak does this need to be based on Lesley's I2C branch? For review it would be easier if it was just the SPI changes.

[ABIbreak]

No, I'll rebase off of main

[ABIbreak]

examples/spi/{Makefile, build.zig, build.zig.zon} were directly copied from the examples/i2c/, I will edit them later

[midnightveil]

Should probably use numbered error codes (ETIMEOUT? idk); instead of int returns.

[omeh-a]

Should probably use numbered error codes (ETIMEOUT? idk); instead of int returns.

This is used internally and there's only one error case in this function, so I don't think this is necessary. We don't have a standard way of going about this though .... probably something we should write into the engineering docs 😳

[midnightveil]

as above re: error codes.

[omeh-a]

If this is an index, is it intended that the cmd_in_progress is a smalelr type than num_cmds?

[omeh-a]

Should probably use numbered error codes (ETIMEOUT? idk); instead of int returns.

This is used internally and there's only one error case in this function, so I don't think this is necessary. We don't have a standard way of going about this though .... probably something we should write into the engineering docs 😳