ifconfig: Add SR-IOV VF status output

• Adds SR-IOV VF status to the existing ifconfig "-v" output
• Adds ioctl command for reporting VF status info from drivers
• Adds support to iflib for drivers to handle this new ioctl
• Add support for ioctl in ixl(4)

Signed-off-by: Eric Joyner <erj@freebsd.org>

Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D19647