nvme: Add NVMEF helper macro as the inverse of NVMEV

This macro accepts a field name and a value for the field and
constructs the shifted field value.

Reviewed by: chuck
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D43604

(cherry picked from commit 3a477a9b70a34dc0686630599c27f022b1e07bd8)