arm: at91: siemens: Add support to generate combined SPL+U-Boot image

This patch adds the necessary defines to the Siemens AT91SAM based
boards (smartweb, corvus and taurus) to generate the combined binary
image with SPL and main U-Boot image combined (u-boot-with-spl.bin).

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Heiko Schocher <hs@denx.de>
Cc: Andreas Bießmann <andreas@biessmann.org>
Cc: Eugen Hristev <eugen.hristev@microchip.com>
Reviewed-by: Heiko Schocher <hs@denx.de>
Tested on the taurus board:
Tested-by: Heiko Schocher <hs@denx.de>
diff --git a/include/configs/taurus.h b/include/configs/taurus.h
index 1d24577..3582eb2 100644
--- a/include/configs/taurus.h
+++ b/include/configs/taurus.h
@@ -173,4 +173,7 @@
 #define CONFIG_SYS_MCKR_CSS		(0x02 | CONFIG_SYS_MCKR)
 #define CONFIG_SYS_AT91_PLLB		0x10193F05
 
+#define CONFIG_SPL_PAD_TO		CONFIG_SYS_NAND_U_BOOT_OFFS
+#define CONFIG_SYS_SPL_LEN		CONFIG_SPL_PAD_TO
+
 #endif