ARM: dts: Configure SmartReflex only to idle the interconnect target module

The TRM has marked dra7 SmartReflex as reserved and we should not
touch those registers as pointed out by Nishanth Menon <nm@ti.com>.
We do still want to idle the related interconnect target modules on
init though.

Let's do this by only configuring the generic interconnect target modules
and not add the child SmartReflex devices.

Cc: Lokesh Vutla <lokeshvutla@ti.com>
Cc: Nishanth Menon <nm@ti.com>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>