Mark functions as static

Mark functions used only in the same translation unit as static. This
only includes functions that do not have a prototype in a header file
either.

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/zfs/dmu_objset.c

@@ -392,7 +392,7 @@ dnode_hash(const objset_t *os, uint64_t obj)
 	return (crc);
 }
 
-unsigned int
+static unsigned int
 dnode_multilist_index_func(multilist_t *ml, void *obj)
 {
 	dnode_t *dn = obj;