jtag: remove minidriver code and minidriver-dummy

jtag: remove minidriver code and minidriver-dummy

With zy1000 removed, there is no other implementation that uses
the minidriver, apart from the test/example minidriver-dummy.
While the idea of the minidriver is probably still valid (that is
to intercept jtag primitives before serialization), there is no
current use case, no guarantee it is really working, and the way
it was implemented (by macros and #if conditionals) is really hard
to maintain and test.

Let's let it rip in git history, from where it could eventually be
taken back in a more modern implementation.
The entry points of minidriver API are still in the code with the
original names.

Change-Id: I882e32cb26cf5842f9cba14e3badaf8948e3760d
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/6091
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>