LU-9814 ldiskfs: restore simple_strtol in prealloc

LU-9814 ldiskfs: restore simple_strtol in prealloc

Since kstrtol needs a null-terminor string so we
back to use simple_strtol in prealloc patches.

Lustre-change: https://review.whamcloud.com/28553
Lustre-commit: 685ef61f0fb9849e3f7a32c4ebf2980d3300afb0

Signed-off-by: Yang Sheng <yang.sheng@intel.com>
Change-Id: I331308d830fbeef9c00156bb8c14b43651d66420
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Alexey Lyashkov <c17817@cray.com>
Signed-off-by: Minh Diep <minh.diep@intel.com>
Reviewed-on: https://review.whamcloud.com/29733
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>