i2c-designware: i2c_dw_xfer_msg can be static

i2c_dw_xfer_msg is only called internally so it can be static. It
original was, before the driver split. No idea why it was changed at
that time.

Signed-off-by: Jean Delvare <[e-mail]>
Acked-by: Dirk Brandewie <[e-mail]>

drivers/i2c/busses/i2c-designware-core.c

···
  * messages into the tx buffer.  Even if the size of i2c_msg data is
  * longer than the size of the tx buffer, it handles everything.
  */
-void
+static void
 i2c_dw_xfer_msg(struct dw_i2c_dev *dev)
 {
 	struct i2c_msg *msgs = dev->msgs;