lpc32xx: Kconfig: switch to CONFIG_CONS_INDEX

There's nothing special or unique to the lpc32xx that requires its own config
parameter for specifying the console uart index. Therefore instead of using
the lpc32xx-specific CONFIG_SYS_LPC32XX_UART include parameter, use the
already-available CONFIG_CONS_INDEX from Kconfig.

Signed-off-by: Trevor Woerner <twoerner@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/mach-lpc32xx/devices.c b/arch/arm/mach-lpc32xx/devices.c
index e1e2e0d..0a4fef2 100644
--- a/arch/arm/mach-lpc32xx/devices.c
+++ b/arch/arm/mach-lpc32xx/devices.c
@@ -23,8 +23,7 @@
 		return;
 
 	/* Disable loopback mode, if it is set by S1L bootloader */
-	clrbits_le32(&ctrl->loop,
-		     UART_LOOPBACK(CONFIG_SYS_LPC32XX_UART));
+	clrbits_le32(&ctrl->loop, UART_LOOPBACK(uart_id));
 
 	if (uart_id < 3 || uart_id > 6)
 		return;