i2c: pmcmsp: fix error return from master_xfer

Returning -1 (-EPERM) is not appropriate here, go with -EIO.
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Fixes: 1b144df1 ("i2c: New PMC MSP71xx TWI bus driver")

drivers/i2c/busses/i2c-pmcmsp.c

@@ -564,7 +564,7 @@ static int pmcmsptwi_master_xfer(struct i2c_adapter *adap,
 		 * TODO: We could potentially loop and retry in the case
 		 * of MSP_TWI_XFER_TIMEOUT.
 		 */
-		return -1;
+		return -EIO;
 	}
 
 	return num;