cobalt/clock: dovetail: provide backend code to CLOCK_HOST_REALTIME

Signed-off-by: hongzha1 <hongzhan.chen@intel.com>

include/cobalt/kernel/dovetail/pipeline/clock.h

@@ -7,6 +7,7 @@
 
 #include <cobalt/uapi/kernel/types.h>
 #include <cobalt/kernel/assert.h>
+#include <linux/ktime.h>
 
 struct timespec64;
 
@@ -52,7 +53,7 @@ static inline const char *pipeline_clock_name(void)
 static inline int pipeline_get_host_time(struct timespec64 *tp)
 {
 	/* Convert ktime_get_real_fast_ns() to timespec. */
-	TODO();
+	*tp = ktime_to_timespec64(ktime_get_real_fast_ns());
 
 	return 0;
 }