FOS: network-failure debug output + drop unused NBD driver

[mastacontrola]

Two small cleanups:

Network-failure debug output (fixes #42, supersedes #77)

When S40network runs out of interfaces without reaching the FOG server, it now prints:

• kernel version and init version
• lspci -nn network devices — the [vendor:device] IDs are exactly what we need to identify a missing driver
• lshw -c network -businfo — also catches USB NICs and unclaimed hardware

The boot banner now shows the kernel version as well. This makes "no NIC driver" reports like #110 self-diagnosing instead of needing a debug-mode round trip with the reporter. Credit to @rluzuriaga for the original idea in #77 — that PR predates the recent funcs.sh refactoring, so this re-implements it on current master.

Sample output on failure:

Debug information (please include this when reporting network issues):
   Kernel version: 6.12.35
   Init version: 20260305
   Network hardware on the PCI bus:
      00:1f.6 Ethernet controller [0200]: Intel Corporation 400 Series Chipset Family GbE Controller [8086:0d4c]
   Network hardware seen by lshw:
      Bus info          Device        Class          Description
      ==========================================================
      pci@0000:00:1f.6  eno2          network        400 Series Chipset Family GbE Controller

Both lspci (pciutils) and lshw are already built into the rootfs on all three arches.

Remove NBD from the kernel configs (fixes #71)

CONFIG_BLK_DEV_NBD=y has been set since the early days but nothing uses it — the rootfs builds no nbd userspace tools and no FOS script references it. Disabled on x64/arm64/x86 as discussed in #71.

Verified: bash -n on both scripts, the debug block exercised live, and tests/golden/run.sh check passes byte-identical.

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