drm/lima: avoid error task dump attempt when not enabled

Currently when users try to run an application with lima and that hits
an issue such as a timeout, a message saying "fail to save task state"
and "error task list is full" is shown in dmesg.

The error task dump is a debug feature disabled by default, so the
error task list is usually not going to be available at all.
The message can be misleading and creates confusion in bug reports.

We can avoid that code path and that particular message when the user
has not explicitly set the max_error_tasks parameter to enable the
feature.

Signed-off-by: Erico Nunes <nunes.erico@gmail.com>
Reviewed-by: Qiang Yu <yuq825@gmail.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Qiang Yu <yuq825@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220209093700.30901-1-nunes.erico@gmail.com