drm/i915: add render state initialization

drm/i915: add render state initialization

HW guys say that it is not a cool idea to let device
go into rc6 without proper 3d pipeline state.

For each new uninitialized context, generate a
valid null render state to be run on context
creation.

This patch introduces a skeleton with empty states.

v2: - No need to vmap (Chris Wilson)
    - use .c files for state (Daniel Vetter)
    - no need to flush as i915_add_request does it
    - remove parameter for batch alloc size
    - don't wait for the init (Ben Widawsky)

v3: - move to cpu/gpu (Chris Wilson)

Tested-by: Kristen Carlson Accardi <[email protected]> (v1)
Tested-by: Oscar Mateo <[email protected]>
Reviewed-by: Damien Lespiau <[email protected]>
Signed-off-by: Mika Kuoppala <[email protected]>
Signed-off-by: Daniel Vetter <[email protected]>