7500 Simplify dbuf_free_range by removing dn_unlisted_l0_blkid
With the integration of: commit 0f6d88aded0d165f5954688a9b13bac76c38da84 Author: Alex Reece <email@example.com> Date: Sat Jul 26 13:40:04 2014 -0800 4873 zvol unmap calls can take a very long time for larger datasets the dnode's dn_bufs field was changed from a list to a tree. As a result, the dn_unlisted_l0_blkid field is no longer necessary.
Author: Stephen Blinick <firstname.lastname@example.org>
Reviewed by: Matthew Ahrens <email@example.com>
Reviewed by: Dan Kimmel <firstname.lastname@example.org>
Approved by: Gordon Ross <email@example.com>