i965: Delete update_renderbuffer_surface flags.

i965: Delete update_renderbuffer_surface flags.

We don't need yet another set of flags.  The function already has access
to both brw and the unit, so it can check brw->draw_aux_buffer_disabled
itself in one line of code.  The layered flag was only used to assert
that Gen4-5 doesn't do layered rendering, which isn't that useful.

Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>