devel/openocd: Overhaul Makefile

Major overhaul after taking over maintainership.

Background information to understand some of the changes: OpenOCD is a piece
of software which talks to chip programming/debugging adapters (hardware).
Different adapters use different interface to connect to the host OS (such as
USB).

• Previously, the port provided one option per upstream supported adapter. This was changed to a "per-interface" option as we mostly care about handling dependencies rather than sequezing out every single byte of the resulting binary size.

• Upstream's doxygen documentation has been removed from this port as this particular piece of documentation is almost entirely only relevant when doing development work on upstream code. The man page is still being installed (unchanged).

• Adding more options previously not exposed by the port.

• The various VERBOSE_ options are not combined into a single option as the amount of information would be overwhelming and not necessarily helpful.

• A local patch to resolve the broken Aarch64 build would be possible but up- stream has removed the offending piece of code since their last release. As such, this patch would be obsolete on the next release and existing users of this port are already "used" to this restriction.

Approved by: zirias (mentor)
Differential Revision: https://reviews.freebsd.org/D44067