if_bnxt: Pluggable Module Display Support

This update enables the display of pluggable module information
to users via the ifconfig utility.

Reviewed by: imp
Approved by: imp
Differential revision: https://reviews.freebsd.org/D42958

(cherry picked from commit 3320f0f69f06df5c36daa8ff71e0c07908ff0f1a)