dmaengine: idxd: Make max batch size attributes in sysfs invisible for Intel IAA

dmaengine: idxd: Make max batch size attributes in sysfs invisible for Intel IAA

In current code, dev.max_batch_size and wq.max_batch_size attributes in
sysfs are exposed to user to show or update the values.

>From Intel IAA spec [1], Intel IAA does not support batch processing. So
these sysfs attributes should not be supported on IAA device.

Fix this issue by making the attributes of max_batch_size invisible in
sysfs through is_visible() filter when the device is IAA.

Add description in the ABI documentation to mention that the attributes
are not visible when the device does not support batch.

[1]: https://cdrdv2.intel.com/v1/dl/getContent/721858

Fixes: e7184b159dd3 ("dmaengine: idxd: add support for configurable max wq batch size")
Fixes: c52ca478233c ("dmaengine: idxd: add configuration component of driver")
Signed-off-by: Xiaochen Shen <xiaochen.shen@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Fenghua Yu <fenghua.yu@intel.com>
Link: https://lore.kernel.org/r/20220930201528.18621-3-xiaochen.shen@intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>