spi: spi-mem: Check the controller extra capabilities

Controllers can now provide a spi-mem capabilities structure. Let's make
use of it in spi_mem_controller_default_supports_op(). As we want to
check for DTR operations as well as normal operations in a single
helper, let's pull the necessary checks from spi_mem_dtr_supports_op()
for now.

However, because no controller provide these extra capabilities, this
change has no effect so far.
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Pratyush Yadav <p.yadav@ti.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/linux-mtd/20220127091808.1043392-3-miquel.raynal@bootlin.com

drivers/spi/spi-mem.c

@@ -173,11 +173,20 @@ EXPORT_SYMBOL_GPL(spi_mem_dtr_supports_op);
 bool spi_mem_default_supports_op(struct spi_mem *mem,
 				 const struct spi_mem_op *op)
 {
-	if (op->cmd.dtr || op->addr.dtr || op->dummy.dtr || op->data.dtr)
-		return false;
+	struct spi_controller *ctlr = mem->spi->controller;
+	bool op_is_dtr =
+		op->cmd.dtr || op->addr.dtr || op->dummy.dtr || op->data.dtr;
 
-	if (op->cmd.nbytes != 1)
-		return false;
+	if (op_is_dtr) {
+		if (!spi_mem_controller_is_capable(ctlr, dtr))
+			return false;
+
+		if (op->cmd.nbytes != 2)
+			return false;
+	} else {
+		if (op->cmd.nbytes != 1)
+			return false;
+	}
 
 	return spi_mem_check_buswidth(mem, op);
 }