remoteproc: xlnx: Avoid RPU force power down

remoteproc: xlnx: Avoid RPU force power down

Powering off RPU using force_pwrdwn call results in system failure
if there are multiple users of that RPU node. Better mechanism is to use
request_node and release_node EEMI calls. With use of these EEMI calls,
platform management controller will take-care of powering off RPU
when there is no user.

Signed-off-by: Tanmay Shah <tanmay.shah@amd.com>
Link: https://lore.kernel.org/r/20250506165944.1109534-1-tanmay.shah@amd.com
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>