drivers: fpga: move to POST_KERNEL

Devices should be initialized either in pre-Kernel or post-Kernel
stages.

Signed-off-by: Gerard Marull-Paretas <gerard@teslabs.com>

drivers/fpga/fpga_eos_s3.c

@@ -148,5 +148,5 @@ static const struct fpga_driver_api eos_s3_api = {
 	.get_info = eos_s3_fpga_get_info
 };
 
-DEVICE_DT_DEFINE(DT_NODELABEL(fpga0), &eos_s3_fpga_init, NULL, &fpga_data, NULL, APPLICATION,
+DEVICE_DT_DEFINE(DT_NODELABEL(fpga0), &eos_s3_fpga_init, NULL, &fpga_data, NULL, POST_KERNEL,
 	      CONFIG_FPGA_INIT_PRIORITY, &eos_s3_api);

drivers/fpga/fpga_zynqmp.c

@@ -323,4 +323,4 @@ static const struct fpga_driver_api zynqmp_api = {
 };
 
 DEVICE_DT_INST_DEFINE(0, &zynqmp_fpga_init, NULL, &fpga_data, NULL,
-	      APPLICATION, CONFIG_FPGA_INIT_PRIORITY, &zynqmp_api);
+	      POST_KERNEL, CONFIG_FPGA_INIT_PRIORITY, &zynqmp_api);