MAINTAINERS: dt: update reference for arm-integrator.txt

This file was renamed. Update references accordingly.

Fixes: 78c7d8f9

 ("dt-bindings: clock: Create YAML schema for ICST clocks")

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lkml.kernel.org/r/491d2928a47f59da3636bc63103a5f63fec72b1a.1584966325.git.mchehab+huawei@kernel.org
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>