As discussed in D6262 post-commit review, change inp_route to
inp_route6 for IPv6 code after r301217.
This was most likely a c&p error from the legacy IP code, which
did not matter as it is a union and both structures have the same
layout at the beginning.
No functional changes.

Reviewed by: karels, ae
Approved by: re (rgrimes)
Differential Revision: https://reviews.freebsd.org/D17005