arm64: dts: ti: iot2050: Disable SR2.0-only PRUs

The IOT2050 devices described so far are using SR1.0 silicon, thus do
not have the additional PRUs of the ICSSG of the SR2.0. Disable them.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Acked-by: Aswath Govindraju <a-govindraju@ti.com>
Acked-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Link: https://lore.kernel.org/r/189a91866fb1af02e4fd2345dc56774aa069d5ba.1632657917.git.jan.kiszka@web.de