drm/amdgpu: add ring buffer information in devcoredump

Add relevant ringbuffer information such as
rptr, wptr,rb mask, ring name, ring size and also
the rings content for each ring on a gpu reset.

Signed-off-by: Sunil Khatri <sunil.khatri@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>