spi: spi-fsl-lpspi: Set correct chip-select polarity bit

[ Upstream commit cbe33705864ba2697a2939de715b81538cf32430 ]

The driver currently supports multiple chip-selects, but only sets the
polarity for the first one (CS 0). Fix it by setting the PCSPOL bit for
the desired chip-select.

Fixes: 5314987d ("spi: imx: add lpspi bus driver")
Signed-off-by: Larisa Grigore <larisa.grigore@nxp.com>
Signed-off-by: James Clark <james.clark@linaro.org>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20250828-james-nxp-lpspi-v2-2-6262b9aa9be4@linaro.org


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