block: Remove unused BlockReopenQueueEntry.perms_checked

This field has been unused since commit 72373e40 ('block:
bdrv_reopen_multiple: refresh permissions on updated graph').
Remove it.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20230911094620.45040-2-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>