intel_iommu: Fix typo in comments

Fix typo:
*Unknwon  ==> Unknown
*futher  ==> further
*configed  ==> configured

Signed-off-by: Cai Huoqing <caihuoqing@baidu.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Message-Id: <20210730014942.2311-1-caihuoqing@baidu.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>