tests: basic ring<->cpu and ring<->ring tests

tests: basic ring<->cpu and ring<->ring tests

Using a dummy reloc that doesn't matter to trick the kernel into
synchroizing the rings.

v2: properly apply MI_NOOP workaround to MI_FLUSH_DW and
switch to MI_COND_BATCH_BUFFER_END as a dummy command on the
render ring to avoid PIPE_CONTROL errata.

v3: somebody clever decided that in C, you cound from 1,
i.e. I915_EXEC_RENDER == 1. It works now ...

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>