drm/nouveau: fix a use-after-free in r535_gsp_rpc_push()

The RPC container is released after being passed to r535_gsp_rpc_send().

When sending the initial fragment of a large RPC and passing the
caller's RPC container, the container will be freed prematurely. Subsequent
attempts to send remaining fragments will therefore result in a
use-after-free.

Allocate a temporary RPC container for holding the initial fragment of a
large RPC when sending. Free the caller's container when all fragments
are successfully sent.

Fixes: 176fdcbd ("drm/nouveau/gsp/r535: add support for booting GSP-RM")
Signed-off-by: Zhi Wang <zhiw@nvidia.com>
Link: https://lore.kernel.org/r/20250527163712.3444-1-zhiw@nvidia.com


[ Rebase onto Blackwell changes. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>