drm/amdgpu: limit the amdgpu_vm_update_ptes trace point

The text output should not be more than a page, so only print the first
32 page table entries.

If we need all of them we can still look into the binary trace.

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