Remove extraneous altq header files

At some point during stable/10, the headers altq_codel.h and
altq_fairq.h where added to /usr/include/altq, before all of altq
was moved to /usr/include/net/altq.

Reviewed by: rpaulo
Approved by: rpaulo
Differential Revision: https://reviews.freebsd.org/D6596