x86: ich-spi: Clear atomic preop only when SPI settings are not locked

The atomic preop register can only be written when SPI settings are
not locked, otherwise it's read-only.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>

drivers/spi/ich.c

@@ -563,7 +563,8 @@ static int ich_spi_xfer(struct udevice *dev, unsigned int bitlen,
 	}
 
 	/* Clear atomic preop now that xfer is done */
-	ich_writew(ctlr, 0, ctlr->preop);
+	if (!lock)
+		ich_writew(ctlr, 0, ctlr->preop);
 
 	return 0;
 }