dt-bindings: remoteproc: k3-r5f: Update bindings for AM64x SoCs

The K3 AM64x SoCs have two dual-core Arm R5F clusters/subsystems, with
2 R5F cores each, both in the MAIN voltage domain.

These clusters are a revised IP version compared to those present on
J721E and J7200 SoCs, and supports a new "Single-CPU" mode instead of
LockStep mode. Update the K3 R5F remoteproc bindings with the compatible
info relevant to these R5F clusters/subsystems on K3 AM64x SoCs.

Signed-off-by: Suman Anna <s-anna@ti.com>