drm/amdgpu: cleanup gmc_v10_0_process_interrupt a bit

Return early in case of a ratelimit and don't print leading zeros for
the address.

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