qdsp-start: add support for 4.9 remoteproc implementation

In kernel 4.9 (and upstream) the remoteproc implementation was changed, and we
should now use /sys/class/remoteproc instead of debugfs. This patch adds
supports for remoteproc instances in /sys/class/remoteproc and falls back to the
old implementation, so that it should be backward compatible.

Signed-off-by: Nicolas Dechesne <nicolas.dechesne@linaro.org>