mtd: rawnand: oxnas: Keep track of registered devices

All initialized and registered devices should be listed somewhere so
that we can unregister/free them in the _remove() path.

This patch is not a fix per-se but is needed to apply three other
fixes coming right after, explaining the Fixes/Cc: stable tags.

Fixes: 6685924924 ("mtd: nand: Add OX820 NAND Support")
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200519130035.1883-36-miquel.raynal@bootlin.com

drivers/mtd/nand/raw/oxnas_nand.c

@@ -32,6 +32,7 @@ struct oxnas_nand_ctrl {
 	void __iomem *io_base;
 	struct clk *clk;
 	struct nand_chip *chips[OXNAS_NAND_MAX_CHIPS];
+	unsigned int nchips;
 };
 
 static uint8_t oxnas_nand_read_byte(struct nand_chip *chip)
@@ -79,7 +80,6 @@ static int oxnas_nand_probe(struct platform_device *pdev)
 	struct nand_chip *chip;
 	struct mtd_info *mtd;
 	struct resource *res;
-	int nchips = 0;
 	int count = 0;
 	int err = 0;
 
@@ -145,12 +145,12 @@ static int oxnas_nand_probe(struct platform_device *pdev)
 			goto err_release_child;
 		}
 
-		oxnas->chips[nchips] = chip;
-		++nchips;
+		oxnas->chips[oxnas->nchips] = chip;
+		++oxnas->nchips;
 	}
 
 	/* Exit if no chips found */
-	if (!nchips) {
+	if (!oxnas->nchips) {
 		err = -ENODEV;
 		goto err_clk_unprepare;
 	}