iommu/amd: Signedness bug in acpihid_device_group()

"devid" needs to be signed for the error handling to work.

Fixes: b097d11a ('iommu/amd: Manage iommu_group for ACPI HID devices')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>