iommu/amd: Remove protection_domain.dev_cnt variable

iommu/amd: Remove protection_domain.dev_cnt variable

protection_domain->dev_list tracks list of attached devices to
domain. We can use list_* functions on dev_list to get device count.
Hence remove 'dev_cnt' variable.

No functional change intended.

Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Reviewed-by: Joerg Roedel <jroedel@suse.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20241030063556.6104-4-vasant.hegde@amd.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>