i3c: dw: Return the length from a read priv_xfer

We currently assume that the rx_len of a read command will be as
submitted, but we may have a shorter read than expected.

This change populates the output i3c xfer length from the actually-read
length.
Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Link: https://lore.kernel.org/r/f4fff7ab18dee1f662dc7a5a4111fcd921e6792b.1680156630.git.jk@codeconstruct.com.auSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/i3c/master/dw-i3c-master.c

@@ -887,6 +887,13 @@ static int dw_i3c_master_priv_xfers(struct i3c_dev_desc *dev,
 	if (!wait_for_completion_timeout(&xfer->comp, XFER_TIMEOUT))
 		dw_i3c_master_dequeue_xfer(master, xfer);
 
+	for (i = 0; i < i3c_nxfers; i++) {
+		struct dw_i3c_cmd *cmd = &xfer->cmds[i];
+
+		if (i3c_xfers[i].rnw)
+			i3c_xfers[i].len = cmd->rx_len;
+	}
+
 	ret = xfer->ret;
 	dw_i3c_master_free_xfer(xfer);