driver list: add source files which register multiple drivers
Add the driver_67.c source file which conditionally registers driver 6
and/or driver 7 (or none if both are disabled). Inclusion is controlled
by the config header file which is controlled by autoconf or cmake user
adjustable options.
Add the driver_8.c source file which registers multiple drivers under a
common condition. External build rules are not aware (and need not be)
that one source file results in multiple driver registrations.