Add include files for prototypes

Include the header with prototypes in the file that provides definitions
as well, to catch any mismatch between prototype and definition.

Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Closes #10470

module/os/freebsd/spl/spl_vm.c

@@ -31,6 +31,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/byteorder.h>
 #include <sys/lock.h>
 #include <sys/freebsd_rwlock.h>
+#include <sys/vm.h>
 
 #include <vm/vm.h>
 #include <vm/vm_param.h>