dm: fpga: Introduce new uclass

For future DM based FPGA drivers and for now to have a meaningful
logging class for old FPGA drivers.

Suggested-by: Michal Simek <michal.simek@amd.com>
Suggested-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Alexander Dahl <post@lespocky.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Link: https://lore.kernel.org/r/20220930120430.42307-2-post@lespocky.de
Signed-off-by: Michal Simek <michal.simek@amd.com>
diff --git a/arch/sandbox/dts/test.dts b/arch/sandbox/dts/test.dts
index 4ee4712..a7b49f3 100644
--- a/arch/sandbox/dts/test.dts
+++ b/arch/sandbox/dts/test.dts
@@ -652,6 +652,10 @@
 		};
 	};
 
+	fpga {
+		compatible = "sandbox,fpga";
+	};
+
 	pinctrl-gpio {
 		compatible = "sandbox,pinctrl-gpio";