x86: baytrail: Add option to disable the internal UART to setup_early_uart()

This patch adds a parameter to the function setup_early_uart() to either
enable or disable the internal BayTrail legacy UART. Since the name
setup_early_uart() does not match its functionality any more, lets
rename it to setup_internal_uart() as well in this patch.

Signed-off-by: Stefan Roese <sr@denx.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/cpu/baytrail/early_uart.c b/arch/x86/cpu/baytrail/early_uart.c
index b64a3a9..471d592 100644
--- a/arch/x86/cpu/baytrail/early_uart.c
+++ b/arch/x86/cpu/baytrail/early_uart.c
@@ -59,11 +59,15 @@
 }
 
 /* This can be called after memory-mapped PCI is working */
-int setup_early_uart(void)
+int setup_internal_uart(int enable)
 {
-	/* Enable the legacy UART hardware. */
+	/* Enable or disable the legacy UART hardware */
 	x86_pci_write_config32(PCI_DEV_CONFIG(0, LPC_DEV, LPC_FUNC), UART_CONT,
-			       1);
+			       enable);
+
+	/* All done for the disable part, so just return */
+	if (!enable)
+		return 0;
 
 	/*
 	 * Set up the pads to the UART function. This allows the signals to