spi: Kconfig: fix a spelling mistake & hyphenation

Correct a spelling mistake (reported by codespell).
Also hyphenate "8-bit".

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: linux-spi@vger.kernel.org
Link: https://lore.kernel.org/r/20230124233502.23330-1-rdunlap@infradead.org


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