drm/i915: always use RPNSWREQ for turbo change requests

commit 89ba829e38bd500f438bc08af4229204c8ed7f35 upstream.

Media turbo requests can either use RPVSWREQ or RPNSWREQ to indicate
what the interrupt handler should do.  Since we only deal with the
latter in our turbo code, make the media engine use that for turbo
requests.

Tested-by: Joe Bloggsian <joebloggsian@gmail.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>