The predicate source registers are needed to implement conditional
rendering without stalling. The two source registers are used to load
the previous values of the PS_DEPTH_COUNT register saved from
PIPE_CONTROL commands. These can then be compared and used to set the
predicate enable bit via the MI_PREDICATE command.

The command parser version number is increased to 2 to make it easier
to detect the new functionality in user space.
Signed-off-by: Neil Roberts <neil@linux.intel.com>
Reviewed-by: Brad Volkin <bradley.d.volkin@intel.com> (v1)
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org> (v1)
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>