qcacmn: Add timekeeping.h inclusion under correct kernel version

timekeeping.h is available from kernel version 3.17. Add header
inclusion and ktime_get_boot_ns call under correct version check flag.

Change-Id: I2a1a127e1716b52af56d14c39e2e646e34b05fa3
CRs-Fixed: 2230949

qdf/inc/qdf_time.h

@@ -168,19 +168,11 @@ static inline qdf_time_t qdf_get_system_uptime(void)
  * The time since system booted in nanoseconds
  */
 
-#if (LINUX_VERSION_CODE > KERNEL_VERSION(3, 10, 0))
-static inline s64 qdf_get_bootbased_boottime_ns(void)
+static inline uint64_t qdf_get_bootbased_boottime_ns(void)
 {
-	return ktime_get_boot_ns();
+	return __qdf_get_bootbased_boottime_ns();
 }
 
-#else
-static inline s64 qdf_get_bootbased_boottime_ns(void)
-{
-	return ktime_to_ns(ktime_get_boottime());
-}
-#endif
-
 /**
  * qdf_get_system_timestamp - Return current timestamp
  *