fdisk: Add support for fixing MBR partitions CHS values

fdisk: Add support for fixing MBR partitions CHS values

Add a new extended option 'F' to fdisk which recalculates and fixes CHS
values for each partition in MBR table according to current fdisk settings
for number of heads and sectors per track.

This allows in interactive mode to repair existing partitions to be
compatible with CHS addressing after changing extended option 'h' (number
of heads) or 's' (sectors per track) as these options do not modify content
of existing partitions.

Signed-off-by: Pali Rohár <pali.rohar@gmail.com>