doc: Remove duplicated documentation directory

Commit ad7061ed74 ("doc: Move device tree bindings documentation to
 doc/device-tree-bindings") moved all device tree binding documentation
to doc/device-tree-bindings directory.

The current U-Boot project still have two documentation directories:

- doc/
- Documentation/

Move all documentation and sphinx files to doc directory so all content
can be in a common place.

Signed-off-by: Breno Lima <breno.lima@nxp.com>

doc/device-tree-bindings/misc/misc/gdsys,soc.txt

@@ -0,0 +1,16 @@
+gdsys soc bus driver
+
+This driver provides a simple interface for the busses associated with gdsys
+IHS FPGAs. The bus itself contains devices whose register maps are contained
+within the FPGA's register space.
+
+Required properties:
+- fpga: A phandle to the controlling IHS FPGA
+
+Example:
+
+FPGA0BUS: fpga0bus {
+	compatible = "gdsys,soc";
+	ranges = <0x0 0xe0600000 0x00004000>;
+	fpga = <&FPGA0>;
+};