net: Add a missing word

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/core/dev.c

@@ -6293,7 +6293,7 @@ EXPORT_SYMBOL(__napi_schedule);
  *	@n: napi context
  *
  * Test if NAPI routine is already running, and if not mark
- * it as running.  This is used as a condition variable
+ * it as running.  This is used as a condition variable to
  * insure only one NAPI poll instance runs.  We also make
  * sure there is no pending NAPI disable.
  */