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

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: 0fa20cdfcc1f ("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>