spi: spi-mem: Compute length only when needed

When adjust_op_size is defined, len is never used. Move the len
computation where it's actually used.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20200228160735.1565047-1-tudor.ambarus@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-mem.c

@@ -418,12 +418,13 @@ int spi_mem_adjust_op_size(struct spi_mem *mem, struct spi_mem_op *op)
 	struct spi_controller *ctlr = mem->spi->controller;
 	size_t len;
 
-	len = sizeof(op->cmd.opcode) + op->addr.nbytes + op->dummy.nbytes;
-
 	if (ctlr->mem_ops && ctlr->mem_ops->adjust_op_size)
 		return ctlr->mem_ops->adjust_op_size(mem, op);
 
 	if (!ctlr->mem_ops || !ctlr->mem_ops->exec_op) {
+		len = sizeof(op->cmd.opcode) + op->addr.nbytes +
+		      op->dummy.nbytes;
+
 		if (len > spi_max_transfer_size(mem->spi))
 			return -EINVAL;