nvme_disk: Use a recursive lock instead of a mutex.

It appears on some controllers we can wind up in cases that are
a double-lock, otherwise.

Should fix #18093.

libnvme: Export controller SGL support in nvme_ctrlr_stat.

libnvme has routines to convert SGL requests into PRP ones,
but they can only go so far, so some requests are truly
SGL-only.

libnvme: Import.

Minor modifications for Haiku included, and for the most part marked
as such.