007-pbp2k (tested): external USB keyboards work

Everything in 007-pbp2j (backlight fix, dim Tow-Boot screen, overlays, 1 s countdown, btrfs, stack fix, fast USB start, SD at 50 MHz, touchpad fix, XHCI fixes, keyboard fallback), plus:

• External USB keyboards work in the Tow-Boot menu, next to the internal one (Tow-Boot#153). Every USB keyboard registered as usbkbd and U-Boot looked keyboards up by that name, so only the first one (the internal keyboard) was ever read. Patch 0023 gives each keyboard its own name and reads each one.
  • Use the right USB-A port, and pick "Rescan USB" first (only the internal keyboard's controller starts at power-on). The left (USB 3) port can't take a keyboard (no interrupt-queue support for XHCI in U-Boot).

Status: tested on my Pinebook Pro (2026-10-13): boots from SPI (power-on to kernel 17.8 s, unchanged); after "Rescan USB" the internal keyboard and a USB keyboard in the right port both work. Not tested: a device in the USB 3 port during a rescan, booting from a USB stick, the SD card installer image.

If you ever saved Tow-Boot settings (saveenv/fw_setenv), run env default -a; saveenv after flashing.

6713b4c7c7e06e5b2b5050edad79d3f211febf6260db0dbab9f66b161a3719d3  Tow-Boot.spi.bin
efa8ec1ef9981534ed37ce59e738c52d7b886c6f8f5584777fae4feac1977d7d  spi.installer.img
66b22088ec0215c285d386492f5f3202efcabf28d11171e7386eddf9e36c2b3a  spi.installer.img.xz