tests: Align zephyr,psa-crypto-rng node names with those used by SoCs

This is a follow-up to commit 9951971a.

Align names of "zephyr,psa-crypto-rng" compatible nodes used in tests
(crypto/rand32 and drivers/entropy/api) with those introduced by the
above commit into SoC definitions (nRF5340/nRF9160). This way the test
overlays will overwrite the already existing nodes instead of adding
second instances of them, what leads to build failures at the linking
stage as the related driver supports only single instance (and creates
it for the first node found).

Signed-off-by: Andrzej Głąbek <andrzej.glabek@nordicsemi.no>