Re-enable atomic tearing capability support

Since DRM_CAP_ATOMIC_ASYNC_PAGE_FLIP capability is now available in the mainline kernel, we should enable back async page flip tearing support. Now drm device supports atomic async page flips.

On top of 3e4aff6a, 9203d98f & !1058 (merged)

This section is Updated

Validated Async flip or tearing support E2E (Weston + Kernel drm-tip). Below are some screenshots for tearing/Async flip enabled vs disabled:

Signed-off-by: Naveen Kumar naveen1.kumar@intel.com