linuxkpi: Add `seq_hex_dump()`

[dumbbell]

Summary

It is a copy of print_hex_dump() but uses a struct sbuf as the destination.

The amdgpu DRM driver started to use it in Linux 6.8.

This is part of the update of DRM drivers to Linux 6.8.

Sponsored by: The FreeBSD Foundation

[bz]

Alternatively I quickly hacked this up -- I don't know which one would be preferable: https://reviews.freebsd.org/D49637

sys/compat/linuxkpi/common/src/linux_seq_file.c

317

For all of these printfs with prefix_str you need an extra %s and check (prefix_str != NULL) ? " " : "" to get the extra space after

320

I think the original implementation of print_hex_dump() got switched to #tx on purpose

[dumbbell]

Superseded by D49637.