greybus: svc: add a "watchdog" to check the network health

Now that we have a svc ping command, let's add a watchdog to call it
every so often (1 second at the moment.)  If it finds something went
wrong, post a stern message to the kernel log and call:
	start unipro_reset
to reset the whole greybus hardware subsystem.

Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Reviewed-by: Rui Miguel Silva <rui.silva@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>