LU-9868 llite: Get rid of ll_dcompare

LU-9868 llite: Get rid of ll_dcompare

The problem with real_lookup, and real_lookup itself are long gone,
so let's kick out invalid dentries in revalidate now.

Change-Id: Ieb274645245a19ac4917e0ec4643a0c44aa32cd3
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Reviewed-on: https://review.whamcloud.com/24175
Reviewed-by: Neil Brown <neilb@suse.de>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>