ARM: dts: imx6qdl-apalis: Change to "adi,force-bt656-4"

ARM: dts: imx6qdl-apalis: Change to "adi,force-bt656-4"

According to adv7180.yaml, the correct property name is
"adi,force-bt656-4".

Update it accordingly to fix several dt-schema warnings:

adv7280@21: 'adv,force-bt656-4' does not match any of the regexes: ...

imx6qdl-apalis.dtsi is the only in-tree kernel user of this property.

BSD does have a adv7180 driver, so should not be impacted.

Signed-off-by: Fabio Estevam <festevam@denx.de>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>