iommu/amd: Fix alias device DTE setting

Commit 7bea695a restructured DTE flag handling but inadvertently changed
the alias device configuration logic. This may cause incorrect DTE settings
for certain devices.

Add alias flag check before calling set_dev_entry_from_acpi(). Also move the
device iteration loop inside the alias check to restrict execution to cases
where alias devices are present.

Fixes: 7bea695a ("iommu/amd: Introduce struct ivhd_dte_flags to store persistent DTE flags")
Cc: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>