Remove host binary object drivers from GENERIC

Four drivers (hpt27xx, hptmv, hptnr, hptrr, hpt27xx) include precompiled
binary objects; have users load them as modules if they are needed.

Additional work (i.e., integrating devmatch) required before MFC.

Reviewed by: markj
Relnotes: Yes
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D21865