mtd: spi-nor: enable the debugfs for the partname and partid

This patch adds spi_nor_debugfs_init() for the debugfs initialization.
With this patch, we can read the partname and partid through the
debugfs.

The output of new debugfs nodes on my device are:
cat /sys/kernel/debug/mtd/mtd0/partid
spi-nor:ef6017
cat /sys/kernel/debug/mtd/mtd0/partname
w25q64dw
Signed-off-by: NZhuohao Lee <zhuohao@chromium.org>
Reviewed-by: NBoris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: NTudor Ambarus <tudor.ambarus@microchip.com>

drivers/mtd/spi-nor/spi-nor.c

@@ -4767,6 +4767,16 @@ static int spi_nor_set_addr_width(struct spi_nor *nor)
 	return 0;
 }
 
+static void spi_nor_debugfs_init(struct spi_nor *nor,
+				 const struct flash_info *info)
+{
+	struct mtd_info *mtd = &nor->mtd;
+
+	mtd->dbg.partname = info->name;
+	mtd->dbg.partid = devm_kasprintf(nor->dev, GFP_KERNEL, "spi-nor:%*phN",
+					 info->id_len, info->id);
+}
+
 static const struct flash_info *spi_nor_get_flash_info(struct spi_nor *nor,
 						       const char *name)
 {
@@ -4847,6 +4857,8 @@ int spi_nor_scan(struct spi_nor *nor, const char *name,
 
 	nor->info = info;
 
+	spi_nor_debugfs_init(nor, info);
+
 	mutex_init(&nor->lock);
 
 	/*