spi: dt-bindings: xilinx: Drop type reference on *-bits properties

Properties with standard unit suffixes such as '-bits' don't need a
type.

Cc: Mark Brown <broonie@kernel.org>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: linux-spi@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20210910165945.2852999-1-robh@kernel.org

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

@@ -27,13 +27,11 @@ properties:
 
   xlnx,num-ss-bits:
     description: Number of chip selects used.
-    $ref: /schemas/types.yaml#/definitions/uint32
     minimum: 1
     maximum: 32
 
   xlnx,num-transfer-bits:
     description: Number of bits per transfer. This will be 8 if not specified.
-    $ref: /schemas/types.yaml#/definitions/uint32
     enum: [8, 16, 32]
     default: 8