dmaengine: imx-sdma: Refine spba bus searching in probe

dmaengine: imx-sdma: Refine spba bus searching in probe

There are multi spba-busses for i.MX8M* platforms, if only search for
the first spba-bus in DT, the found spba-bus may not the real bus of
audio devices, which cause issue for sdma p2p case, as the sdma p2p
script presently does not deal with the transactions involving two devices
connected to the AIPS bus.

Search the SDMA parent node first, which should be the AIPS bus, then
search the child node whose compatible string is spba-bus under that AIPS
bus for the above multi spba-busses case.

Fixes: 8391ecf465ec ("dmaengine: imx-sdma: Add device to device support")
Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260407032755.2758049-1-shengjiu.wang@nxp.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>