Prepare for modification of gradient using shader. The
gradient pixmaps now is generated by pixman and we will
replace them with shader. Add structure fields and
dispatch functions which will be needed. Some auxiliary
macro for vertex convert.
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Zhigang Gong <zhigang.gong@linux.intel.com>
Signed-off-by: Zhigang Gong <zhigang.gong@linux.intel.com>