dt-bindings: spi: add reference file to YAML

In JH7110 SoC, the spi module needs to use "arm,primecell-periphid" to
override the h/w ID value to correctly init "spi_dev", so add
"primecell.yaml" as the reference file for YAML.

Signed-off-by: William Qiu <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

Documentation/devicetree/bindings/spi/spi-pl022.yaml

···
 
 allOf:
   - $ref: spi-controller.yaml#
+  - $ref: /schemas/arm/primecell.yaml#
 
 # We need a select here so we don't match all nodes with 'arm,primecell'
 select: