LU-6142 mdt: Fix style issues for mdt_identity.c

LU-6142 mdt: Fix style issues for mdt_identity.c

This patch fixes issues reported by checkpatch
for file lustre/mdt/mdt_identity.c

Test-Parameters: trivial
Signed-off-by: Arshad Hussain <arshad.super@gmail.com>
Change-Id: Ifb7f51ae4bdc8ab7dd816411a8017c379b298763
Reviewed-on: https://review.whamcloud.com/38928
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Ben Evans <beevans@whamcloud.com>
Reviewed-by: Petros Koutoupis <petros.koutoupis@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>