at91: cleanup taurus port

- at91sam9g20-taurus.dts: use labels
- cleanup taurus port to compile clean with
  current mainline again. SPL has no serial
  output anymore, so it fits into SRAM.

Signed-off-by: Heiko Schocher <hs@denx.de>
diff --git a/board/siemens/taurus/Kconfig b/board/siemens/taurus/Kconfig
index cf71e4c..28816bc 100644
--- a/board/siemens/taurus/Kconfig
+++ b/board/siemens/taurus/Kconfig
@@ -9,4 +9,20 @@
 config SYS_CONFIG_NAME
 	default "taurus"
 
+choice
+	prompt "Board Type AXM/TAURUS"
+	default BOARD_AXM
+
+config BOARD_AXM
+	bool "AXM board type"
+	help
+	  Select this, if you want to build for AXM board.
+
+config BOARD_TAURUS
+	bool "TAURUS board type"
+	help
+	  Select this, if you want to build for TAURUS board.
+
+endchoice
+
 endif