dma_intel: fix ats_disable attribute handling

dma_intel: fix ats_disable attribute handling

Some DSA devices allow the Address Translation Service (ATS) to be
controlled at the workqueue level. For those devices, the ats_disable
attribute is exposed in sysfs. For devices that do not support ATS
control per workqueue, and are driven by an idxd kernel driver >= 6.6,
the ats_disable attribute is not visible in sysfs.

This change fixes the DSA workqueue initialization to handle the case
where the ats_disable sysfs attribute is not present.

Type: fix

Change-Id: Ia11a90686b9e1916ab50a4209b67f3270190c3f1
Signed-off-by: Jeff Shaw <[email protected]>