spi: cadence: Change dt-bindings documentation for Cadence XSPI contr…

…oller

Interrupt property is not mandatory.
Driver will switch into pooling mode if property
will not be avalible.

Signed-off-by: Witold Sadowski <wsadowski@marvell.com>

Documentation/devicetree/bindings/spi/cdns,xspi.yaml

@@ -40,7 +40,6 @@ properties:
 required:
   - compatible
   - reg
-  - interrupts
 
 unevaluatedProperties: false