sandybridge: Native gfx init.

Change-Id: I07590086ffe3b1d068fa6ae6b156039cc2e55893
Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-on: http://review.coreboot.org/6755
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>