ktls: Drop all the INET and INET6 compile-time guards.

Consistent with 9fd0d9b16e93ff2a3bd375a98763dca0150dcee0, KERN_TLS is
not supported on kernels without any INET support.

Reviewed by: gallatin, hselasky
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D39232