fpga: region: fix use-after-free in child_regions_with_firmware()

Move of_node_put(child_region) after the error print to avoid accessing
freed memory when pr_err() references child_region.

Fixes: 0fa20cdfcc ("fpga: fpga-region: device tree control for FPGA")
Cc: stable@vger.kernel.org
Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
[ Yilun: Fix the Fixes tag ]
Reviewed-by: Xu Yilun <yilun.xu@intel.com>
Link: https://lore.kernel.org/r/20260408154534.404327-1-vulab@iscas.ac.cn
Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>

drivers/fpga/of-fpga-region.c

@@ -168,11 +168,10 @@ static int child_regions_with_firmware(struct device_node *overlay)
 						     fpga_region_of_match);
 	}
 
-	of_node_put(child_region);
-
 	if (ret)
 		pr_err("firmware-name not allowed in child FPGA region: %pOF",
 		       child_region);
+	of_node_put(child_region);
 
 	return ret;
 }