habanalabs: rename user_ctx as compute_ctx

This patch renames the "user_ctx" field in the device structure to
"compute_ctx". This better reflects the meaning of this context.

In addition, we also check in the ctx_fini() that the debug mode should be
disabled only if the context being destroyed is the compute context. This
has no effect right now as we only have a single process and a single
context, but this makes the code more ready for multiple process support.

Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>