drm/amdgpu: Add check to prevent IH overflow

drm/amdgpu: Add check to prevent IH overflow

Similar to commit <81ce6b9e81d6>("drm/amdgpu: fix IH overflow on Vega10 v2").
When an ring buffer overflow happens the appropriate bit is set in the WPTR
register which is also written back to memory. But clearing the bit in the
WPTR doesn't trigger another memory writeback.

So what can happen is that we end up processing the buffer overflow over and
over again because the bit is never cleared. Resulting in a random system
lockup because of an infinite loop in an interrupt handler.

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Defang Bo <bodefang@126.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>