mtd: sf: Make sure we don't register the same device twice

spi_flash_mtd_register() can be called several times and each time it
will register the same mtd_info instance like if it was a new one.
The MTD ID allocation gets crazy when that happens, so let's track the
status of the sf_mtd_info object to avoid that.

Fixes: 9fe6d871 ("mtd, spi: Add MTD layer driver")
Signed-off-by: NBoris Brezillon <boris.brezillon@bootlin.com>
Tested-by: NHeiko Schocher <hs@denx.de>
Reviewed-by: NJagan Teki <jagan@openedev.com>

drivers/mtd/spi/sf_mtd.c

@@ -10,6 +10,7 @@
 #include <spi_flash.h>
 
 static struct mtd_info sf_mtd_info;
+static bool sf_mtd_registered;
 static char sf_mtd_name[8];
 
 static int spi_flash_mtd_erase(struct mtd_info *mtd, struct erase_info *instr)
@@ -73,6 +74,12 @@ static int spi_flash_mtd_number(void)
 
 int spi_flash_mtd_register(struct spi_flash *flash)
 {
+	int ret;
+
+	if (sf_mtd_registered)
+		del_mtd_device(&sf_mtd_info);
+
+	sf_mtd_registered = false;
 	memset(&sf_mtd_info, 0, sizeof(sf_mtd_info));
 	sprintf(sf_mtd_name, "nor%d", spi_flash_mtd_number());
 
@@ -94,7 +101,11 @@ int spi_flash_mtd_register(struct spi_flash *flash)
 	sf_mtd_info.numeraseregions = 0;
 	sf_mtd_info.erasesize = flash->sector_size;
 
-	return add_mtd_device(&sf_mtd_info);
+	ret = add_mtd_device(&sf_mtd_info);
+	if (!ret)
+		sf_mtd_registered = true;
+
+	return ret;
 }
 
 void spi_flash_mtd_unregister(void)