CVE-2026-31439 dmaengine: xilinx: xdma: Fix regmap init error handling

In the Linux kernel, the following vulnerability has been resolved: dmaengine: xilinx: xdma: Fix regmap init error handling devmregmapinitmmio returns an ERRPTR upon error, not NULL. Fix the error check and also fix the error message. Use the error code from ERRPTR instead of the wrong value in r...