dmaengine: idxd: Add wq occupancy information to sysfs attribute

Add occupancy information to wq sysfs attribute. Attribute will show
wq occupancy data if "WQ Occupancy Support" field in WQCAP is 1. It
displays the number of entries currently in this WQ. This is provided
as an estimate and should not be relied on to determine whether there
is space in the WQ. The data is to provide information to user apps
for flow control.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/162275745546.1857062.8765615879420582018.stgit@djiang5-desk3.ch.intel.com


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