qcow2: Fix QCOW2_COMPRESSED_SECTOR_MASK

Masks for L2 table entries should have 64 bit.

Fixes: b6c24694
Buglink: https://bugs.launchpad.net/qemu/+bug/1850000


Cc: qemu-stable@nongnu.org
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20191028161841.1198-2-mreitz@redhat.com
Reviewed-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
(cherry picked from commit 24552feb)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>