mtd: rawnand: Add a helper to check supported operations

Let's use a helper to clearly check if an operation is supported or not.

Return -ENOTSUPP when ->exec_op() is not implemented as we cannot know.
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://lore.kernel.org/linux-mtd/20200507105241.14299-8-miquel.raynal@bootlin.com

drivers/mtd/nand/raw/internals.h

@@ -109,6 +109,15 @@ static inline bool nand_has_exec_op(struct nand_chip *chip)
 	return true;
 }
 
+static inline int nand_check_op(struct nand_chip *chip,
+				const struct nand_operation *op)
+{
+	if (!nand_has_exec_op(chip))
+		return 0;
+
+	return chip->controller->ops->exec_op(chip, op, true);
+}
+
 static inline int nand_exec_op(struct nand_chip *chip,
 			       const struct nand_operation *op)
 {