habanalabs: add userptr_lookup node in debugfs

It is useful to have the ability to see which user address was pinned
to which physical address during the initial mapping. We already have
all that info stored, but no means to search this data (which may be
quite large).

Signed-off-by: Yuri Nudelman <ynudelman@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>