iommu/vt-d: Remove BUG_ON on checking valid pfn range

When encountering an unexpected invalid pfn range, the kernel should
attempt recovery and proceed with execution. Therefore, using WARN_ON to
replace BUG_ON to avoid halting the machine.

Besides, one redundant checking is reduced.

Signed-off-by: Tina Zhang <tina.zhang@intel.com>
Link: https://lore.kernel.org/r/20230406065944.2773296-3-tina.zhang@intel.com


Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>