LU-6142 mtd: use tabs to indent struct mdt_thread_info

Prior to a (small) code change, change indenting of
struct mtd_thread_info to consistently use TABs.

Test-Parameters: trivial
Signed-off-by: Mr NeilBrown <neilb@suse.com>
Change-Id: Ic0f29a8b84640862294610e37a941b77292446e7
Reviewed-on: https://review.whamcloud.com/35920
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Shaun Tancheff <stancheff@cray.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.super@gmail.com>