soc/intel/common/uart: Only return valid UART base

We only configure the base address for the console UART, the other
addresses are never assigned to the hardware. It seems better to
return 0 for them instead of a spurious value.

Change-Id: I3fa5c99958b56ca5b0b603917c086bdddb677fa2
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/33096
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Lance Zhao <lance.zhao@gmail.com>

src/soc/intel/common/block/uart/uart.c

@@ -46,8 +46,9 @@ static void uart_lpss_init(uintptr_t baseaddr)
 #if CONFIG(DRIVERS_UART_8250MEM)
 uintptr_t uart_platform_base(int idx)
 {
-	/* return Base address for UART console index */
+	if (idx == CONFIG_UART_FOR_CONSOLE)
-	return UART_BASE_0_ADDR(idx);
+		return UART_BASE_0_ADDR(CONFIG_UART_FOR_CONSOLE);
+	return 0;
 }
 #endif