drivers: spi: Add driver for smartbond

This adds the SPI driver for the Renesas SmartBond(tm) DA1469x MCU family.
The driver only supports controller mode. All four SPI modes are supported.
Note that the lowest supported speed is 2285714Hz.
Requesting speeds higher than 16MHz, will result in a 16MHz SCLK.

Co-authored-by: Stan Geitel <stan@geitel.nl>

Signed-off-by: Ben Lauret <ben.lauret.wm@renesas.com>