Remove dead code

Delete unused functions.

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/ddt.c

@@ -594,12 +594,6 @@ ddt_decompress(uchar_t *src, void *dst, size_t s_len, size_t d_len)
 		byteswap_uint64_array(dst, d_len);
 }
 
-ddt_t *
-ddt_select_by_checksum(spa_t *spa, enum zio_checksum c)
-{
-	return (spa->spa_ddt[c]);
-}
-
 ddt_t *
 ddt_select(spa_t *spa, const blkptr_t *bp)
 {

module/zfs/zrlock.c

@@ -156,15 +156,6 @@ zrl_exit(zrlock_t *zrl)
 	mutex_exit(&zrl->zr_mtx);
 }
 
-int
-zrl_refcount(zrlock_t *zrl)
-{
-	ASSERT3S(zrl->zr_refcount, >, ZRL_DESTROYED);
-
-	int n = (int)zrl->zr_refcount;
-	return (n <= 0 ? 0 : n);
-}
-
 int
 zrl_is_zero(zrlock_t *zrl)
 {