media: venus: firmware: Use iommu_paging_domain_alloc()

An iommu domain is allocated in venus_firmware_init() and is attached to
core->fw.dev in the same function. Use iommu_paging_domain_alloc() to
make it explicit.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20240610085555.88197-10-baolu.lu@linux.intel.com


Signed-off-by: Stanimir Varbanov <stanimir.k.varbanov@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>