fdisk: fix alignment check for non-512-byte logical sectors

fdisk: fix alignment check for non-512-byte logical sectors

 # modprobe scsi_debug dev_size_mb=1024 sector_size=4096

 # fdisk /dev/sdb

  Command (m for help): n
  Command action
    e   extended
    p   primary partition (1-4)
  p
  Partition number (1-4, default 1):
  Using default value 1
  First sector (256-262143, default 256): 257
  Last sector, +sectors or +size{K,M,G} (257-262143, default 262143): +100M

  Command (m for help): p

  Disk /dev/sdb: 1073 MB, 1073741824 bytes
  32 heads, 32 sectors/track, 256 cylinders, total 262144 sectors
  Units = sectors of 1 * 4096 = 4096 bytes
  Sector size (logical/physical): 4096 bytes / 4096 bytes
  I/O size (minimum/optimal): 4096 bytes / 262144 bytes
  Disk identifier: 0x16db2bb0

    Device Boot      Start         End      Blocks   Id  System
  /dev/sdb1            257       25855      102396   83  Linux
  Partition 1 does not start on physical sector boundary.
  ^^^^^^^^

 The warning is nonsense. The logical and physical sector size is the
 same. It means that every LBA is always aligned to physical sector
 boundary.

 Note that this bug does not mean that fdisk produces unaligned
 partitions. The problem is that fdisk forces to use bigger gaps
 between aligned LBAs, for example:

   correctly aligned LBA are: 256, 257, 258, ...  [N+1]
   fdisk assumes:             256, 264, 272, ...  [N+(sector_size/512)]

Reported-by: JOB NELSON <job_nelson@hotmail.com>
Signed-off-by: Karel Zak <kzak@redhat.com>