radeonsi: set drirc compiler options before calling common screen init

radeonsi: set drirc compiler options before calling common screen init

Also, access the options directly, allowing us to get rid of the
PIPE_SCREEN_xxx flags.

Tested-by: Dieter Nützel <Dieter@nuetzel-hh.de>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>