disk/nvme: Update copyright headers

Most of the code is a port of FreeBSD's NVMe's driver, made by Jim
Harris (Intel).

Though all subsequent contributions that happened on this original
driver were made on files copyrighted by Intel, and under BSD-2 clause,
let's update the copyright header to point out Jim's original work and
major contributors were relevant.

Signed-off-by: Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>