serial: Add new config option SPL_DEBUG_UART_BASE

SPL_DEBUG_UART_BASE is same as DEBUG_UART_BASE, but applies only for SPL.

In some cases base address of UART is different in SPL and proper U-Boot.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index 26fa498..46726d7 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -508,6 +508,13 @@
 	  A default should be provided by your board, but if not you will need
 	  to use the correct value here.
 
+config SPL_DEBUG_UART_BASE
+	hex "Base address of UART for SPL"
+	depends on SPL && DEBUG_UART
+	default DEBUG_UART_BASE
+	help
+	  This is the base address of your UART for memory-mapped UARTs for SPL.
+
 config DEBUG_UART_CLOCK
 	int "UART input clock"
 	depends on DEBUG_UART