qcow2: Rename BDRVQcowState to BDRVQcow2State BDRVQcowState is already used by qcow1, and gdb is always confused which one to use. Rename the qcow2 one so they can be distinguished. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Alberto Garcia <berto@igalia.com>