dt-bindings: mtd: partitions: Drop partitions.yaml

dt-bindings: mtd: partitions: Drop partitions.yaml

The partitions.yaml schema is an unusual structure in that it includes
all possible partition types, and it disables the normal matching by
compatible strings. As partitions.yaml has nothing to match on, it is
only applied when explicitly referenced. The use of "oneOf" also results
in misleading warnings which are difficult to understand. Drop
partitions.yaml and rely on the standard compatible matching instead.

The "mmc-card" case previously allowed any partition type, but now only
allows "fixed-partitions". There aren't any users and the original
intent appeared to be only for "fixed-partitions".

Acked-by: Ulf Hansson <ulf.hansson@linaro.org> # For MMC
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>