dmg: use uint64_t consistently for sectors and lengths

dmg: use uint64_t consistently for sectors and lengths

The DMG metadata is stored as uint64_t, so use the same type for
sector_num.  int was a particularly poor choice since it is only 32-bit
and would truncate large values.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit 686d7148ec23402a172628c800022b3a95a022c9)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>