phy: qcom-qmp-usb: clean up device-tree parsing

phy: qcom-qmp-usb: clean up device-tree parsing

Since the QMP driver split there will be at most a single child node so
drop the obsolete iteration construct.

While at it, drop the verbose error logging that would have been
printed also on probe deferrals.

Note that there's no need to check if there are additional child nodes
(the kernel is not a devicetree validator), but let's return an error if
there are no child nodes at all for now.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20221028160435.26948-7-johan+linaro@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>