arm64: dts: mediatek: mt8173-elm: Fix MT6397 PMIC sub-node names

arm64: dts: mediatek: mt8173-elm: Fix MT6397 PMIC sub-node names

The MT6397 PMIC bindings specify exact names for its sub-nodes. The
names used in the current dts don't match, causing a validation error.

Fix up the names. Also drop the label for the regulators node, since
any reference should be against the individual regulator sub-nodes.

Fixes: 689b937bedde ("arm64: dts: mediatek: add mt8173 elm and hana board")
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20241210092614.3951748-1-wenst@chromium.org
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>