This adds a helper to check whether a device needs to
use bounce buffer. It also provides a boot time option
to disable the bounce buffer. Users can use this to
prevent the iommu driver from using the bounce buffer
for performance gain.

Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: NLu Baolu <baolu.lu@linux.intel.com>
Tested-by: NXu Pengfei <pengfei.xu@intel.com>
Tested-by: NMika Westerberg <mika.westerberg@intel.com>
Signed-off-by: NJoerg Roedel <jroedel@suse.de>