arm64: dts: imx8mn: Fix duplicate node name

Error log:
sysfs: cannot create duplicate filename '/bus/platform/devices/30000000.bus'

The spba bus name is duplicate with aips bus name.
Refine spba bus name to fix this issue.

Fixes: 970406ea

 ("arm64: dts: imx8mn: Enable Asynchronous Sample Rate Converter")
Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>