memory: tegra: Read client ID on GART page fault

With the device tree binding changes, now Memory Controller has access to
GART registers. Hence it is now possible to read client ID on GART page
fault to get information about what memory client causes the fault.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>