spi: lpspi: run transfer speed_hz sanity check

Avoid config.speed_hz is 0 when it is a divisor.

Signed-off-by: Han Xu <han.xu@nxp.com>
Signed-off-by: Clark Wang <xiaoning.wang@nxp.com>
Link: https://lore.kernel.org/r/20230505064159.3964473-1-xiaoning.wang@nxp.com


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