dt-bindings: media: nxp,imx7-mipi-csi2: Drop bad if/then schema

The if/then schema for 'data-lanes' doesn't work as 'compatible' is at a
different level than 'data-lanes'. To make it work, the if/then schema
would have to be moved to the top level and then whole hierarchy of
nodes down to 'data-lanes' created. I don't think it is worth the
complexity to do that, so let's just drop it.

The error in this schema is masked by a fixup in the tools causing the
'allOf' to get overwritten. Removing the fixup as part of moving to
json-schema draft 2019-09 revealed the issue:

Documentation/devicetree/bindings/media/nxp,imx7-mipi-csi2.example.dt.yaml: mipi-csi@30750000: ports:port@0:endpoint:data-lanes:0: [1] is too short
	From schema: /builds/robherring/linux-dt-review/Documentation/devicetree/bindings/media/nxp,imx7-mipi-csi2.yaml
Documentation/devicetree/bindings/media/nxp,imx7-mipi-csi2.example.dt.yaml: mipi-csi@32e30000: ports:port@0:endpoint:data-lanes:0: [1, 2, 3, 4] is too long
	From schema: /builds/robherring/linux-dt-review/Documentation/devicetree/bindings/media/nxp,imx7-mipi-csi2.yaml

The if condition was always true because 'compatible' did not exist in
'endpoint' node and a non-existent property is true for json-schema.

Fixes: 85b62ff2cb ("media: dt-bindings: media: nxp,imx7-mipi-csi2: Add i.MX8MM support")
Cc: Rui Miguel Silva <rmfrfs@gmail.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: NXP Linux Team <linux-imx@nxp.com>
Cc: linux-media@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Rui Miguel Silva <rmfrfs@gmail.com>
Link: https://lore.kernel.org/r/20211203164828.187642-1-robh@kernel.org

Documentation/devicetree/bindings/media/nxp,imx7-mipi-csi2.yaml

@@ -79,6 +79,8 @@ properties:
 
             properties:
               data-lanes:
+                description:
+                  Note that 'fsl,imx7-mipi-csi2' only supports up to 2 data lines.
                 items:
                   minItems: 1
                   maxItems: 4
@@ -91,18 +93,6 @@ properties:
             required:
               - data-lanes
 
-            allOf:
-              - if:
-                  properties:
-                    compatible:
-                      contains:
-                        const: fsl,imx7-mipi-csi2
-                then:
-                  properties:
-                    data-lanes:
-                      items:
-                        maxItems: 2
-
       port@1:
         $ref: /schemas/graph.yaml#/properties/port
         description: