ARM: kirkwood: reduce dependence of including platform file

For files like the drivers/serial/serial.c, it must include the
platform file, as the CONFIG_SYS_NS16550_COM1 must reference to the
definition in the platform definition files.

Include the platform definition file in the config file, so that it
would decouple the dependence for the driver files.

Signed-off-by: Lei Wen <leiwen@marvell.com>
diff --git a/arch/arm/include/asm/arch-kirkwood/config.h b/arch/arm/include/asm/arch-kirkwood/config.h
index b393b1a..f17f82d 100644
--- a/arch/arm/include/asm/arch-kirkwood/config.h
+++ b/arch/arm/include/asm/arch-kirkwood/config.h
@@ -39,6 +39,7 @@
 #error "SOC Name not defined"
 #endif /* CONFIG_KW88F6281 */
 
+#include <asm/arch/kirkwood.h>
 #define CONFIG_ARM926EJS	1	/* Basic Architecture */
 
 #define CONFIG_MD5	/* get_random_hex on krikwood needs MD5 support */