busybox: backport hexdump fix for Big Endian systems

busybox: backport hexdump fix for Big Endian systems

hexdump isn't working properly on some Big Endian systems, producing
incorrect output such as:
  hexdump -vn 5 -e '"fd" 1/1 "%02x:" 2/2 "%x:"' /dev/urandom
  fdff:542c0054:17920017:
Which should be:
  fdff:542c:1792:

This breaks the default ULA prefix generation on some systems. See:
https://github.com/openwrt/openwrt/issues/19844

The issue has already been fixed upstream, so we can backport the fix:
https://git.busybox.net/busybox/commit/libbb/dump.c?id=f5c7cae55fc3e19d074198bc12152486067ea8c7

Signed-off-by: Álvaro Fernández Rojas <[email protected]>