cacheinfo: Decrement refcount in cache_setup_of_node()

Refcounts to DT nodes are only incremented in the function
and never decremented. Decrease the refcounts when necessary.

Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Link: https://lore.kernel.org/r/20221026185954.991547-1-pierre.gondois@arm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>