We've got a report that the runtime PM may make the codec the
unresponsive on AMD platforms.  Since the feature has been tested only
on the recent Intel platforms, it's safer to limit the support to such
devices for now.

This patch adds a new DCAPS bit flag indicating the runtime PM
support, and mark it for Intel controllers.
Reported-and-tested-by: Julian Wollrath <jwollrath@web.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>