drm/amdgpu: cleanup gmc_v9_0_process_interrupt

First of all don't snprintf into a char buffer allocated on the stack with
a constant hubname.

Then cleanup to exit the function early in case of a ratelimit or SRIOV.

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