Atomic ioctl can also send the same page flip flags as legacy ioctl.
In those cases also need to send the vblank event to userspace.

vmwgfx does not support flag DRM_MODE_PAGE_FLIP_ASYNC, so this flag is
never expected.
Signed-off-by: NDeepak Rawat <drawat@vmware.com>
Reviewed-by: NSinclair Yeh <syeh@vmware.com>
Signed-off-by: NThomas Hellstrom <thellstrom@vmware.com>