fpga: x400: Add support for X4C, C1, and UC variants

Moves X4C_100, X4C_200, C1_100, and C1_200 from experimental to
available targets and makes the needed changes to allow them to build
successfully.

Adds support for "UC" FPGA variant. U indicates that QSFP0 is unused
and C indicates that QSFP1 is 100 GbE.

Adds experimental CG_200 variant.


Original-commit: cb9609c886b156e22ae9d879fffad8d060f2ca2d

top/x400/dts/usrp_x410_fpga_UC.dts

@@ -0,0 +1,20 @@
+/*
+ * Copyright 2023 Ettus Research, a National Instruments Brand
+ *
+ * SPDX-License-Identifier: LGPL-3.0-or-later
+ */
+
+/dts-v1/;
+/plugin/;
+
+#include "x410-version-info.dtsi"
+
+#include "x410-fpga.dtsi"
+
+#include "x410-common.dtsi"
+
+#include "x410-rfdc.dtsi"
+
+#include "x410-dma.dtsi"
+
+#include "x410-100gbe-port1.dtsi"