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/obtaining.chapter.md

@@ -0,0 +1,26 @@
+# Obtaining NixOS {#sec-obtaining}
+
+NixOS ISO images can be downloaded from the [NixOS download
+page](https://nixos.org/nixos/download.html). There are a number of
+installation options. If you happen to have an optical drive and a spare
+CD, burning the image to CD and booting from that is probably the
+easiest option. Most people will need to prepare a USB stick to boot
+from. [](#sec-booting-from-usb) describes the preferred method to
+prepare a USB stick. A number of alternative methods are presented in
+the [NixOS Wiki](https://nixos.wiki/wiki/NixOS_Installation_Guide#Making_the_installation_media).
+
+As an alternative to installing NixOS yourself, you can get a running
+NixOS system through several other means:
+
+-   Using virtual appliances in Open Virtualization Format (OVF) that
+    can be imported into VirtualBox. These are available from the [NixOS
+    download page](https://nixos.org/nixos/download.html).
+
+-   Using AMIs for Amazon's EC2. To find one for your region and
+    instance type, please refer to the [list of most recent
+    AMIs](https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/virtualisation/ec2-amis.nix).
+
+-   Using NixOps, the NixOS-based cloud deployment tool, which allows
+    you to provision VirtualBox and EC2 NixOS instances from declarative
+    specifications. Check out the [NixOps
+    homepage](https://nixos.org/nixops) for details.