spi: Stacked/parallel memories bindings

Merge series from Miquel Raynal <miquel.raynal@bootlin.com>:

DT bindings for stacked and parallel flash/memory devices.

base-commit: e783362eb54cd99b2cac8b3a9aeac942e6f6ac07

diff --cc Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml
Simple merge