With 'unevaluatedProperties' support enabled, several SPI based display
binding examples have warnings:

Documentation/devicetree/bindings/display/panel/samsung,ld9040.example.dt.yaml: lcd@0: Unevaluated properties are not allowed ('#address-cells', '#size-cells', 'spi-max-frequency', 'spi-cpol', 'spi-cpha' were unexpected)
Documentation/devicetree/bindings/display/panel/kingdisplay,kd035g6-54nt.example.dt.yaml: panel@0: Unevaluated properties are not allowed ('spi-max-frequency', 'spi-3wire' were unexpected)
Documentation/devicetree/bindings/display/panel/ilitek,ili9322.example.dt.yaml: display@0: Unevaluated properties are not allowed ('reg' was unexpected)
Documentation/devicetree/bindings/display/panel/samsung,s6e63m0.example.dt.yaml: display@0: Unevaluated properties are not allowed ('spi-max-frequency' was unexpected)
Documentation/devicetree/bindings/display/panel/abt,y030xx067a.example.dt.yaml: panel@0: Unevaluated properties are not allowed ('spi-max-frequency' was unexpected)
Documentation/devicetree/bindings/display/panel/sony,acx565akm.example.dt.yaml: panel@2: Unevaluated properties are not allowed ('spi-max-frequency', 'reg' were unexpected)
Documentation/devicetree/bindings/display/panel/tpo,td.example.dt.yaml: panel@0: Unevaluated properties are not allowed ('spi-max-frequency', 'spi-cpol', 'spi-cpha' were unexpected)
Documentation/devicetree/bindings/display/panel/lgphilips,lb035q02.example.dt.yaml: panel@0: Unevaluated properties are not allowed ('reg', 'spi-max-frequency', 'spi-cpol', 'spi-cpha' were unexpected)
Documentation/devicetree/bindings/display/panel/innolux,ej030na.example.dt.yaml: panel@0: Unevaluated properties are not allowed ('spi-max-frequency' was unexpected)
Documentation/devicetree/bindings/display/panel/sitronix,st7789v.example.dt.yaml: panel@0: Unevaluated properties are not allowed ('spi-max-frequency', 'spi-cpol', 'spi-cpha' were unexpected)

Fix all of these by adding a reference to spi-peripheral-props.yaml.
With this, the description that the binding must follow
spi-controller.yaml is both a bit out of date and redundant, so remove
it.
Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Paul Cercueil <paul@crapouillou.net>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://lore.kernel.org/r/20211221125209.1195932-1-robh@kernel.org