LU-8974 osd-ldiskfs: increase supported ldiskfs fs size

LU-8974 osd-ldiskfs: increase supported ldiskfs fs size

Change "force_over_256tb" mount option to "force_over_512tb".

Seagate-bug-id: MRP-4077
Signed-off-by: Artem Blagodarenko <artem.blagodarenko@seagate.com>
Change-Id: I4b0c1d9faf2139f2b4fc4ff94ed78af5e218110d
Reviewed-on: https://review.whamcloud.com/24524
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>