mtd: maps: physmap: Retain mtd-name property from dts

In physmap_flash_of_init() the maps[].name can be populated based on the
optional 'linux,mtd-name' property in the dts. Make sure this is
retained when filling in the rest of the map[] data.
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200824025744.25992-1-chris.packham@alliedtelesis.co.nz

drivers/mtd/maps/physmap-core.c

@@ -515,7 +515,8 @@ static int physmap_flash_probe(struct platform_device *dev)
 		dev_notice(&dev->dev, "physmap platform flash device: %pR\n",
 			   res);
 
-		info->maps[i].name = dev_name(&dev->dev);
+		if (!info->maps[i].name)
+			info->maps[i].name = dev_name(&dev->dev);
 
 		if (!info->maps[i].phys)
 			info->maps[i].phys = res->start;