clk: sandbox: Create a special fixed-rate driver

Create a version of this driver for sandbox so that it can use the
of-platdata struct.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/sandbox/dts/sandbox.dtsi b/arch/sandbox/dts/sandbox.dtsi
index 7455c99..5bf8445 100644
--- a/arch/sandbox/dts/sandbox.dtsi
+++ b/arch/sandbox/dts/sandbox.dtsi
@@ -31,7 +31,7 @@
 
 	clk_fixed: clk-fixed {
 		u-boot,dm-pre-reloc;
-		compatible = "fixed-clock";
+		compatible = "sandbox,fixed-clock";
 		#clock-cells = <0>;
 		clock-frequency = <1234>;
 	};