Include prototypes for vdev_initialize

Address two prototype related warnings emitted by clang.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Igor Kozhukhov <igor@dilos.org>
Signed-off-by: Matt Macy <mmacy@FreeBSD.org>
Closes #9535

module/zfs/vdev_initialize.c

@@ -32,6 +32,7 @@
 #include <sys/dsl_synctask.h>
 #include <sys/zap.h>
 #include <sys/dmu_tx.h>
+#include <sys/vdev_initialize.h>
 
 /*
  * Value that is written to disk during initialization.
@@ -424,7 +425,7 @@ vdev_initialize_load(vdev_t *vd)
  * Convert the logical range into a physical range and add it to our
  * avl tree.
  */
-void
+static void
 vdev_initialize_range_add(void *arg, uint64_t start, uint64_t size)
 {
 	vdev_t *vd = arg;