clk: ti: dra7-atl-clock: fix child-node lookups

Fix child node-lookup during probe, which ended up searching the whole
device tree depth-first starting at parent rather than just matching on
its children.

Note that the original premature free of the parent node has already
been fixed separately, but that fix was apparently never backported to
stable.

Fixes: 9ac33b0c ("CLK: TI: Driver for DRA7 ATL (Audio Tracking Logic)")
Fixes: 660e1551 ("clk: ti: dra7-atl-clock: Fix of_node reference counting")
Cc: stable <stable@vger.kernel.org>     # 3.16: 660e1551
Cc: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Acked-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>