ifconfig: Fix the display of capabilities in the netlink based code.

The capabilities in if_capabilities2/if_capenable2 are reported in the
second 32b and were not being displayed correctly. v does not need to
be advanced because v[i / 32] is the correct 32b value already.

Sponsored by: Chelsio Communications

Reviewed by: kib@
Differential Revision: https://reviews.freebsd.org/D41107