fpga: region: check for child regions before allocing image info

During a device tree overlay pre-apply notification, the check
for child FPGA regions can happen slightly earlier.  This saves
us from allocating the FPGA image info that just gets thrown
away.

This is a baby step in refactoring the FPGA region code to
separate out common FPGA region code from FPGA region
Device Tree overlay support.
Signed-off-by: Alan Tull <atull@kernel.org>
Acked-by: Moritz Fischer <mdf@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/fpga/fpga-region.c

@@ -355,15 +355,19 @@ static int fpga_region_notify_pre_apply(struct fpga_region *region,
 	const char *firmware_name;
 	int ret;
 
-	info = fpga_image_info_alloc(dev);
-	if (!info)
-		return -ENOMEM;
-
-	/* Reject overlay if child FPGA Regions have firmware-name property */
+	/*
+	 * Reject overlay if child FPGA Regions added in the overlay have
+	 * firmware-name property (would mean that an FPGA region that has
+	 * not been added to the live tree yet is doing FPGA programming).
+	 */
 	ret = child_regions_with_firmware(nd->overlay);
 	if (ret)
 		return ret;
 
+	info = fpga_image_info_alloc(dev);
+	if (!info)
+		return -ENOMEM;
+
 	/* Read FPGA region properties from the overlay */
 	if (of_property_read_bool(nd->overlay, "partial-fpga-config"))
 		info->flags |= FPGA_MGR_PARTIAL_RECONFIG;