In the dt-bindings, "atu" reg-names is required to get the register space
for iATU in Synopsys DWC version 4.80 or later.

Link: https://lore.kernel.org/r/1601444167-11316-2-git-send-email-hayashi.kunihiko@socionext.comSigned-off-by: NKunihiko Hayashi <hayashi.kunihiko@socionext.com>
Signed-off-by: NLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: NRob Herring <robh@kernel.org>