dmaengine: idxd: add support for configurable max wq batch size

Add sysfs attribute max_batch_size to wq in order to allow the max batch
size configured on a per wq basis. Add support code to configure
the valid user input on wq enable. This is a performance tuning
parameter.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/159865273617.29141.4383066301730821749.stgit@djiang5-desk3.ch.intel.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>