drm/amdgpu/ih: store the full context id

The contextID field (formerly known as src_data) of the IH
vector stores client specific information about an interrupt.
It was expanded from 32 bits to 128 on newer asics.  Expand the
src_id field to handle this.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>