Previously the blorp engine only supported RGBA8 color buffers and
24-bit depth buffers.  This patch adds support for any color buffer
format that is supported as a render target, and for 16-bit and 32-bit
depth buffers.

This required threading the brw_context struct through into
brw_blorp_surface_info::set() so that it can consult the
brw->render_target_format array.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>