drm/i915/bdw: dispatch updates (64b related)

drm/i915/bdw: dispatch updates (64b related)

The command to emit batch buffers has changed to address 48b addresses.
It seemed reasonable that we could still use the old instruction where
emitting 0 for length would do the right thing, but it seems to bother
the simulator when the code does that.

Now the second dword in the command has the upper 16b of the address of
the batchbuffer.

v2: Remove duplicated vfun assignment.

v3: Squash in VECS support changes from Zhao Yakui <yakui.zhao@intel.com>

v4: Make checkpatch happy.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net> (v2)
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>