Rename Intel NUC machine to Generic x86-64 (#1209)

* Rename Intel NUC machine to Generic x86-64

The Intel NUC machine has evolved and supports various x86-64 machines
today. Rename the board.

Note that this does not address the migration issue. This will be
handled separately.

* Update Scripts/Documentation

Documentation/boards/generic-x86-64/README.md

@@ -0,0 +1,61 @@
+# Generic x86-64
+
+## Supported Hardware
+
+This board configuration aims to support most x86-64 systems with UEFI boot. The
+main aim is to support Intel NUC mini PCs and similar systems. Hardware it has
+been tested with is listed below.
+
+## Tested Hardware
+
+| Device                | Release Date | Support | Config      |
+|-----------------------|--------------|---------|-------------|
+| Intel NUC5CPYH        | Q3 2015      | yes     | [generic_x86_64](../../../buildroot-external/configs/generic_x86_64_defconfig) |
+| Intel NUC6CAYH        | Q4 2016      | yes     | [generic_x86_64](../../../buildroot-external/configs/generic_x86_64_defconfig) |
+| Intel NUC7i3DNHE	| Q3 2017      | yes     | [generic_x86_64](../../../buildroot-external/configs/generic_x86_64_defconfig) |
+| Intel NUC10i3FNK2     | Q4 2019      | yes     | [generic_x86_64](../../../buildroot-external/configs/generic_x86_64_defconfig) |
+| Gigabyte GB-BPCE-3455 | 2017         | yes*    | [generic_x86_64](../../../buildroot-external/configs/generic_x86_64_defconfig) |
+
+\* needs 'nomodeset' in cmdline.txt if you want a console
+
+
+## Requirements
+
+- x86-64 support
+- UEFI boot
+- SATA/AHCI or eMMC storage
+- Supported NIC:
+  - Intel Gigabit NIC (e1000, igb - via Linux mainline)
+  - Intel PCIe Gigabit NIC (e1000e - via out-of-tree module in *buildroot-external/package/intel-e1000e*)
+  - Realtek Gigabit NIC (r8169)
+  - Intel Wireless Wifi 802.11ac (iwlwifi, see below)
+
+## Wifi
+
+The following cards are supported:
+
+- Intel Wireless 3160
+- Intel Wireless 7260
+- Intel Wireless 7265
+- Intel Wireless-AC 3165
+- Intel Wireless-AC 3168
+- Intel Wireless-AC 8260
+- Intel Wireless-AC 8265
+- Intel Wireless-AC 9260
+- Intel Wireless-AC 9461
+- Intel Wireless-AC 9462
+- Intel Wireless-AC 9560
+
+## Bluetooth
+
+Bluetooth is untested.
+
+## Installation
+
+Make sure secure boot is disabled in the UEFI BIOS settings.
+
+Currently there is no shiny installation method. Checklist:
+- Boot PC to live environment using PXE or USB
+- Copy or download the Home Assistant OS image into your live environment
+- unxz the image and dd to the local hard disk
+- Reboot