drm/amdgpu: Add prescreening stage in IH processing (v2)

To filter out high-frequency interrupts that can be safely ignored.

v2: squash in trivial typo fix for si (Alex)

Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>