nvme-trace: support for fabrics commands in host-side

This patch introduces fabrics commands tracing feature from host-side.
This patch does not include any changes for the previous host-side
tracing, but just add fabrics commands parsing in cmd=() format.

Signed-off-by: Minwoo Im <minwoo.im.dev@gmail.com>
[hch: fixed some whitespace damage]
Signed-off-by: Christoph Hellwig <hch@lst.de>