arm64: dts: meson: Fix erroneous SPI bus warnings

dtc has new checks for SPI buses. The meson dts files have a node named
spi' which causes false positive warnings. As the node is a pinctrl child
node, change the node name to be 'spi-pins' to fix the warnings.

arch/arm64/boot/dts/amlogic/meson-gxbb-nanopi-k2.dtb: Warning (spi_bus_bridge): /soc/periphs@c8834000/pinctrl@4b0/spi: incorrect #address-cells for SPI bus

Cc: Carlo Caione <carlo@caione.org>
Cc: Kevin Hilman <khilman@baylibre.com>
Cc: linux-amlogic@lists.infradead.org
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>

arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi

@@ -390,7 +390,7 @@ mux {
 			};
 		};
 
-		spi_pins: spi {
+		spi_pins: spi-pins {
 			mux {
 				groups = "spi_miso",
 					"spi_mosi",

arch/arm64/boot/dts/amlogic/meson-gxl.dtsi

@@ -337,7 +337,7 @@ mux {
 			};
 		};
 
-		spi_pins: spi {
+		spi_pins: spi-pins {
 			mux {
 				groups = "spi_miso",
 					"spi_mosi",