LU-7334 lprocfs: Allow default multiplier of 1

LU-7334 lprocfs: Allow default multiplier of 1

A new default unit '1' is accepted by lprocfs_str_with_units_to_s64
to indicate a default multiplier of 1.

Signed-off-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Change-Id: Iebf29f5d3c36e583729ea717288850729b99eeed
Reviewed-on: http://review.whamcloud.com/20455
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Christopher J. Morrone <morrone2@llnl.gov>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>