uboot: (firmwareOdroidC2/C4) don't invoke patch tool, use patches = [] instead

https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/generic/setup.sh#L948
this can do it nicely.

Signed-off-by: Anton Arapov <anton@deadbeef.mx>

nixos/doc/manual/installation/installing-pxe.section.md

@@ -0,0 +1,32 @@
+# Booting from the "netboot" media (PXE) {#sec-booting-from-pxe}
+
+Advanced users may wish to install NixOS using an existing PXE or iPXE
+setup.
+
+These instructions assume that you have an existing PXE or iPXE
+infrastructure and simply want to add the NixOS installer as another
+option. To build the necessary files from your current version of nixpkgs,
+you can run:
+
+```ShellSession
+nix-build -A netboot.x86_64-linux '<nixpkgs/nixos/release.nix>'
+```
+
+This will create a `result` directory containing: \* `bzImage` -- the
+Linux kernel \* `initrd` -- the initrd file \* `netboot.ipxe` -- an
+example ipxe script demonstrating the appropriate kernel command line
+arguments for this image
+
+If you're using plain PXE, configure your boot loader to use the
+`bzImage` and `initrd` files and have it provide the same kernel command
+line arguments found in `netboot.ipxe`.
+
+If you're using iPXE, depending on how your HTTP/FTP/etc. server is
+configured you may be able to use `netboot.ipxe` unmodified, or you may
+need to update the paths to the files to match your server's directory
+layout.
+
+In the future we may begin making these files available as build
+products from hydra at which point we will update this documentation
+with instructions on how to obtain them either for placing on a
+dedicated TFTP server or to boot them directly over the internet.