powerpc/dts: Remove "spidev" nodes

"spidev" is not a real device, but a Linux implementation detail. It has
never been documented either. The kernel has WARNed on the use of it for
over 6 years. Time to remove its usage from the tree.
Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211217221400.3667133-1-robh@kernel.org

arch/powerpc/boot/dts/digsy_mtc.dts

@@ -25,14 +25,6 @@ rtc@800 {
 			status = "disabled";
 		};
 
-		spi@f00 {
-			msp430@0 {
-				compatible = "spidev";
-				spi-max-frequency = <32000>;
-				reg = <0>;
-			};
-		};
-
 		psc@2000 {		// PSC1
 			status = "disabled";
 		};

arch/powerpc/boot/dts/o2d.dtsi

@@ -34,12 +34,6 @@ psc@2000 {		// PSC1
 			#address-cells = <1>;
 			#size-cells = <0>;
 			cell-index = <0>;
-
-			spidev@0 {
-				compatible = "spidev";
-				spi-max-frequency = <250000>;
-				reg = <0>;
-			};
 		};
 
 		psc@2200 {		// PSC2