nouveau/gsp: don't free ctrl messages on errors

It looks like for some messages the upper layers need to get access to the
results of the message so we can interpret it.

Rework the ctrl push interface to not free things and cleanup properly
whereever it errors out.

Requested-by: Lyude
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231222043308.3090089-9-airlied@gmail.com