net: socket: move ktime2ts to ktime header api

Currently, ktime2ts is a small helper function that is only used in
net/socket.c. Move this helper into the ktime API as a small inline
function, so that i) it's maintained together with ktime routines,
and ii) also other files can make use of it. The function is named
ktime_to_timespec_cond() and placed into the generic part of ktime,
since we internally make use of ktime_to_timespec(). ktime_to_timespec()
itself does not check the ktime variable for zero, hence, we name
this function ktime_to_timespec_cond() for only a conditional
conversion, and adapt its users to it.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/ktime.h b/include/linux/ktime.h
index e83512f..bbca128 100644
--- a/include/linux/ktime.h
+++ b/include/linux/ktime.h
@@ -330,6 +330,24 @@
 
 extern ktime_t ktime_add_safe(const ktime_t lhs, const ktime_t rhs);
 
+/**
+ * ktime_to_timespec_cond - convert a ktime_t variable to timespec
+ *			    format only if the variable contains data
+ * @kt:		the ktime_t variable to convert
+ * @ts:		the timespec variable to store the result in
+ *
+ * Returns true if there was a successful conversion, false if kt was 0.
+ */
+static inline bool ktime_to_timespec_cond(const ktime_t kt, struct timespec *ts)
+{
+	if (kt.tv64) {
+		*ts = ktime_to_timespec(kt);
+		return true;
+	} else {
+		return false;
+	}
+}
+
 /*
  * The resolution of the clocks. The resolution value is returned in
  * the clock_getres() system call to give application programmers an