tools: Prune and document tools

Add a tools/README.md.

Remove:

- create_flash_image.py: role now overtaken by tkeyimage which does
  more.
- reset-tk1: Leftover from when production_test was removed.

Rename:

- makehex.py: Moved up one level.

hw/application_fpga/tools/README.md

@@ -0,0 +1,33 @@
+# Tools
+
+We have developed some tools necessary for the build.
+
+- `app_bin_to_spram_hex.py`: Script used to include a device app in a
+  testbench simulation.
+
+- `b2s`: Compute and print a BLAKE2s digest over a file. Used for the
+  digest of the app in app slot 0 included in the firmware.
+
+- `default_partition.bin`: Default partition table for the flash.
+
+- `load_preloaded_app.sh`: Script to load two copies of the partition
+  table to flash and a pre-loaded to app slot 0 or 1. Needs
+  `default_partition.bin`, generated with `tkeyimage` and the binary
+  of the device app to load. Call like: `./load_preloaded_app 0
+  path/to/binary`.
+
+- `makehex.py`: Used to build hex version of firmware ROM for FPGA
+  bitstream build.
+
+- `patch_uds_udi.py`: Script used to patch in the Unique Device Secret
+  in `data/uds.hex` and the Unique Device Identifier in `data/udi.hex`
+  into the bitstream without having to rebuild the entire bitstream.
+
+- `run_pnr.sh`: Script to run place and route with `nextpnr` in order
+  to find a routing seed that will meet desired timing.
+
+- `tkeyimage`: Utility to create and parse flash images with a TKey
+  filesystem or the partition table
+
+- `tpt/tpt.py`: Utility to create the Unique Device Secret (UDS) and
+  Unique Device Identity (UDI) interactively.