arm64: dts: mediatek: mt8186: Change gpu speedbin nvmem cell name

MT8186's GPU speedbin value must be interpreted, or the value will not
be meaningful.
Use the correct "gpu-speedbin" nvmem cell name for the GPU speedbin to
allow triggering the cell info fixup handler, hence feeding the right
speedbin number to the users.

Cc: stable@vger.kernel.org
Fixes: 263d2fd0 ("arm64: dts: mediatek: mt8186: Add GPU speed bin NVMEM cells")
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20231005151150.355536-1-angelogioacchino.delregno@collabora.comSigned-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

arch/arm64/boot/dts/mediatek/mt8186.dtsi

@@ -1656,7 +1656,7 @@ efuse: efuse@11cb0000 {
 			#address-cells = <1>;
 			#size-cells = <1>;
 
-			gpu_speedbin: gpu-speed-bin@59c {
+			gpu_speedbin: gpu-speedbin@59c {
 				reg = <0x59c 0x4>;
 				bits = <0 3>;
 			};