ipc: move Open AMP from lib/ to subsys/ipc/

Moved the Open AMP code from lib/ to subsys/ipc/ to better
organize IPC-related components.

Updated build and config files to reflect the new location.

Adjusted path in MAINTAINERS.yml.

Signed-off-by: Iuliana Prodan <iuliana.prodan@nxp.com>
14 files changed