Currently, the driver has separate logic to determine device coherency
for DT vs ACPI.  This patch simplifies the code with a call to
device_dma_is_coherent().
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>