dt-bindings: remoteproc: do not override firmware-name $ref

dt-bindings: remoteproc: do not override firmware-name $ref

dtschema package defines firmware-name as string-array, so individual
bindings should not make it a string but instead just narrow the number
of expected firmware file names.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20240115182031.1610088-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Bjorn Andersson <andersson@kernel.org>