Use a bitfield to declare vrend_interp_info and make it a fixed size array.
One one hand this avoids all the hassles with allocating and freeing memory,
and it will make it possible to shrink the size of the data that is passed
from the sinfo to the shader key.
Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Rohan Garg <rohan.garg@collabora.com>