dt-bindings: arm: altera: combine Intel's SoCFPGA into altera.yaml

dt-bindings: arm: altera: combine Intel's SoCFPGA into altera.yaml

For all SoCFPGA platforms, whether it has the "intel" or "altr" vendor
prefix are referring to the same business unit that is responsible for
the platform. And now that Altera has spun off to be a separate corporate
entity from Intel, it would make sense to have the device bindings
documentation in the same file.

Move the Intel AgileX board binding documentations into the same file that
contains the Altera ones.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>