scsi: mpi3mr: Fix W=1 compilation warnings

Fix for the following W=1 compilation warning:

  'strncpy' output may be truncated copying 16 bytes from a string of
  length 64

Link: https://lore.kernel.org/r/20210707081756.20922-1-sreekanth.reddy@broadcom.com
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Sreekanth Reddy <sreekanth.reddy@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>