drm/nouveau/gsp: fix potential leak of memory used during acpi init

If any of the ACPI calls fail, memory allocated for the input buffer
would be leaked.  Fix failure paths to free allocated memory.

Also add checks to ensure the allocations succeeded in the first place.

Reported-by: Danilo Krummrich <dakr@kernel.org>
Fixes: 176fdcbd ("drm/nouveau/gsp/r535: add support for booting GSP-RM")
Signed-off-by: Ben Skeggs <bskeggs@nvidia.com>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Link: https://lore.kernel.org/r/20250617040036.2932-1-bskeggs@nvidia.com