drm/amdgpu: add timeout flush mechanism to update wptr for self interrupt (v2)

outstanding log reaches threshold will trigger IH ring1/2's wptr
reported, that will avoid generating interrupts to ring0 too frequent.
But if ring1/2's wptr hasn't been increased for a long time, the outstanding log
can't reach threshold so that driver can't get latest wptr info and
miss some interrupts.

v2: squash in warning fix

Signed-off-by: Chengming Gui <Jack.Gui@amd.com>
Reviewed-by: Feifei Xu <Feifei.Xu@amd.com>
Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>