config.mk: All options in DEFAULTS are now defined in opt_global.h

To simplify management of all the options that should be enabled for the
different architectures, adopt the convention that all options listed in
DEFAULTS will be #defined to 1 in opt_global.h for untied builds. Except
for GEOM_* and ISAPNP, they are all in opt_global.h. ISAPNP is a
opt_dontuse.h, so only filter GEOM_*.

Sponsored by: Netflix
Reviewed by: kevans
Differential Revision: https://reviews.freebsd.org/D37108