powerpc: add CONFIG_SECURE_BOOT condition into fsl_secure_boot.h

This patch is for board config file not to add CONFIG_SECURE_BOOT
condition for include the asm/fsl_secure_boot.h.

Signed-off-by: Po Liu <Po.Liu@freescale.com>
diff --git a/arch/powerpc/include/asm/fsl_secure_boot.h b/arch/powerpc/include/asm/fsl_secure_boot.h
index c36f3c3..4c7f0b1 100644
--- a/arch/powerpc/include/asm/fsl_secure_boot.h
+++ b/arch/powerpc/include/asm/fsl_secure_boot.h
@@ -7,6 +7,7 @@
 #ifndef __FSL_SECURE_BOOT_H
 #define __FSL_SECURE_BOOT_H
 
+#ifdef CONFIG_SECURE_BOOT
 #if defined(CONFIG_FSL_CORENET)
 #define CONFIG_SYS_PBI_FLASH_BASE		0xc0000000
 #else
@@ -15,3 +16,4 @@
 #define CONFIG_SYS_PBI_FLASH_WINDOW		0xcff80000
 
 #endif
+#endif