Added VAEntrypointEncSliceLP for implementations to expose a low power/high performance variant of slice level encoding entrypoint.
Added VAEntrypointEncSliceLP for implementations to expose a low power/high performance variant of slice level encoding entrypoint.

Signed-off-by: Jonathan Bian <9991297f52a6f9abf50455fb144f81941846d99c@intel.com>
Reviewed-By: Sean V Kelley <56c4ee8950656f8ee63ca686448cb9aeaf109ab0@intel.com>
(cherry picked from commit 71030701cef0c1099e87d112f3207cb78a6ce711)

01org/libva-cros,01org/iotg-lin-gfx-libva,01org/libva-cros,01org/iotg-lin-gfx-libva,01org/libva-cros,01org/iotg-lin-gfx-libva