ARM: dts: rmobile: Fix RPC-IF device node names

According to the Generic Names Recommendation in the Devicetree
Specification Release v0.3, and the DT Bindings for the Renesas Reduced
Pin Count Interface, the node name for a Renesas RPC-IF device should be
"spi".  Especially on R-Car Gen3 and RZ/G2, the node name matters, as
the node is enabled by passing a DT fragment from TF-A to U-Boot, and
from U-Boot to subsequent software.

Fix this by renaming the device nodes from "rpc" to "spi".

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
diff --git a/arch/arm/dts/r8a774c0-u-boot.dtsi b/arch/arm/dts/r8a774c0-u-boot.dtsi
index af1c861..f50816a 100644
--- a/arch/arm/dts/r8a774c0-u-boot.dtsi
+++ b/arch/arm/dts/r8a774c0-u-boot.dtsi
@@ -10,7 +10,7 @@
 
 / {
 	soc {
-		rpc: rpc@ee200000 {
+		rpc: spi@ee200000 {
 			compatible = "renesas,rcar-gen3-rpc", "renesas,rpc-r8a774c0";
 			reg = <0 0xee200000 0 0x100>, <0 0x08000000 0 0x04000000>;
 			clocks = <&cpg CPG_MOD 917>;