Imx9 enable lpspi pcs manual control

[jlaitine]

Summary

This PR adds a function imx9_lpspi_select_cs to assert CS at the start of an SPI transfer and keep it asserted until called again to de-assert it. This can be called by board-provided imx9_lpspi_select, in case the CS needs to be controlled via the LPSPI block and not GPIO.

The TCR register CONT (continue) bit is asserted to prevent CS toggling during the transfer, and the PCS bits are set to mark the correct CS

In addition this corrects some TCR register PCS bit definitions which are not valid for IMX9 device. I expect that this is a copy-paste error from some other i.MX platform.

Impact

Impacts only imx9 designs using LPSPI. Doesn't impact existing designs, adds a new feature, enabling to use the internal CS signal of the SPI block.

Testing

Tested on a custom IMX9 board, with icm42605 IMU sensor connected to LPSPI. Previously, had the CS signal muxed to GPIO1_IO11 (IOMUXC_PAD_SAI1_TXFS_GPIO1_IO11), and moved that to internal PCS signal (IOMUXC_PAD_SAI1_TXFS_LPSPI1_PCS0).

Tested in PX4 environment, showing that the sensor in question works:

> listener sensor_gyro -i 2

TOPIC: sensor_gyro instance 2 #1
 sensor_gyro
    timestamp: 13508265 (0.001096 seconds ago)
    timestamp_sample: 13508135 (130 us before timestamp)
    device_id: 2686986 (Type: 0x29, SPI:1 (0x00))
    x: -0.00207
    y: 0.00133
    z: -0.00756
    temperature: 50.4
    error_count: 0
    clip_counter: [0, 0, 0]
    samples: 10