CC13XX/CC26XX board files have the chip select pin set to PIN_UNASSIGNED. When the SPI driver is opened in slave mode, the driver always attempts to configure the CS pin. This fails however, we nothing is done in the driver to address the failure. The PIN should be define in the header file (as IOID_11). The default SPI mode for LPRF board files has changed from 3 pin mode to 4 pin mode to align with other devices and resolve an issue with the default spi example. LPRF devices using SPI in a default configuration will now expect a chip select (CS) line to be connected.