Add few updates to the STM32 SPI driver

Merge series from Clément Le Goffic <clement.legoffic@foss.st.com>:

This series aims to improve the STM32 SPI driver in different areas.
It adds SPI_READY mode, fixes an issue raised by a kernel bot,
add the ability to use DMA-MDMA chaining for RX and deprecate an ST bindings
vendor property.