mtd: spinand: Add missing check

The update cache variant is mandatory, both read and write versions are
being checked, but not this one. All chip drivers seem to implement this
variant, so there should be no breakage.

Reviewed-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Author: miquelraynal

drivers/mtd/nand/spi/core.c

@@ -1430,6 +1430,9 @@ int spinand_match_and_init(struct spinand_device *spinand,
 
 		op = spinand_select_op_variant(spinand,
 					       info->op_variants.update_cache);
+		if (!op)
+			return -ENOTSUPP;
+
 		spinand->op_templates.update_cache = op;
 
 		return 0;