spi: correct spelling

Correct spelling problems for Documentation/spi/ as reported
by codespell.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20230127064005.1558-28-rdunlap@infradead.org


Signed-off-by: Mark Brown <broonie@kernel.org>