libfdisk: clean up sun geometry stuff

 - move fdisk_sun_set_* functions to public API file
 - remove extra function to set ncyl -- this has to follow regular
   geo.cylinders
 - set alternative cylinders to zero (to be compatible with parted)
 - it seems that the previous code completely ignored relation between
   geo.cylinders, sunlabel->acyl and sunlabel->ncyl.

Signed-off-by: Karel Zak <kzak@redhat.com>
fdisk: move geometry commands to separate menu

Signed-off-by: Karel Zak <kzak@redhat.com>
fdisk: add functions to geometry menu

Signed-off-by: Karel Zak <kzak@redhat.com>