Revert "arm64: dts: mediatek: mt8390-genio-common: Add firmware-name for scp0"

Revert "arm64: dts: mediatek: mt8390-genio-common: Add firmware-name for scp0"

As clearly seen on other non-MediaTek platforms, this is known to
eventually produce regressions in the future, as drivers may break
ABI and stop working with older firmware versions.

Although the firmware-name property was used in multiple MediaTek
devicetrees for the System Companion Processor (SCP) node, avoid
doing the same on MT8390 to lessen eventual ABI breakages that may
happen with a driver update to change the firmware retrieval logic
for the SCP.

This reverts commit 2f0066dae66f30386ecd6408410e27a4d6818c15.

Link: https://lore.kernel.org/r/20250520111002.282841-1-angelogioacchino.delregno@collabora.com
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>