dt-bindings: mmc: synopsys-dw-mshc: integrate Altera and Imagination

The bindings for Altera and Imagination extensions are the same as for
the original Synopsys Designware Mobile Storage Host Controller.
Integrate them into Synopsys bindings to have dtschema coverage.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20211227133558.135185-3-krzysztof.kozlowski@canonical.com


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>