gpu: nova-core: preserve error information in gpu_name()

gpu: nova-core: preserve error information in gpu_name()

Change gpu_name() to return a Result instead of an Option. This avoids
silently discarding error information when parsing the GPU name string
from the GSP.

Update the callsite to log a warning with the error details on failure,
rather than just displaying "invalid GPU name".

Suggested-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Link: https://patch.msgid.link/20260108005811.86014-2-jhubbard@nvidia.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>