freebsd: changes necessary to coexist with dtrace in tree

Fix header conflicts when building zfs with openzfs as a vendor import.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@ixsystems.com>
Signed-off-by: Matt Macy <mmacy@FreeBSD.org>
Closes #10497

module/zfs/spa_config.c

@@ -27,6 +27,7 @@
  */
 
 #include <sys/spa.h>
+#include <sys/file.h>
 #include <sys/fm/fs/zfs.h>
 #include <sys/spa_impl.h>
 #include <sys/nvpair.h>