wandboard: Rework Makefile to prevent spl.o from being built

The spl.c source was entirely conditioned by CONFIG_SPL_BUILD.
Change this moving CONFIG_SPL_BUILD to be used in the Makefile,
which is slightly cleaner and more readable.

Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>

board/wandboard/Makefile

@@ -2,4 +2,5 @@
 #
 # (C) Copyright 2013 Freescale Semiconductor, Inc.
 
-obj-y  := wandboard.o spl.o
+obj-y  := wandboard.o
+obj-$(CONFIG_SPL_BUILD) += spl.o

board/wandboard/spl.c

@@ -20,7 +20,6 @@
 #include <asm/arch/sys_proto.h>
 #include <spl.h>
 
-#if defined(CONFIG_SPL_BUILD)
 #include <asm/arch/mx6-ddr.h>
 /*
  * Driving strength:
@@ -513,5 +512,3 @@ int board_mmc_init(bd_t *bis)
 
 	return 0;
 }
-
-#endif