Makefile: doesn't need check stack size when dtb is not built

The commit 5fed97af20da ("Makefile: ensure DTB doesn't overflow into
initial stack") adds an extra check for stack size in BSS if
CONFIG_SYS_INIT_SP_BSS_OFFSET is enabled.
This check, however, doesn't make sense under the configuration where
control dtb won't be built in and it should be void in such cases.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Fixes: 5fed97af20da ("Makefile: ensure DTB doesn't overflow into initial stack")
Reviewed-by: Stephen Warren <swarren@nvidia.com>
diff --git a/Makefile b/Makefile
index 07539ca..fa687f1 100644
--- a/Makefile
+++ b/Makefile
@@ -903,7 +903,7 @@
 ALL-y += $(CONFIG_BUILD_TARGET:"%"=%)
 endif
 
-ifdef CONFIG_INIT_SP_RELATIVE
+ifeq ($(CONFIG_INIT_SP_RELATIVE)$(CONFIG_OF_SEPARATE),yy)
 ALL-y += init_sp_bss_offset_check
 endif
 
@@ -1208,7 +1208,7 @@
 		fi \
 	fi
 
-ifdef CONFIG_INIT_SP_RELATIVE
+ifeq ($(CONFIG_INIT_SP_RELATIVE)$(CONFIG_OF_SEPARATE),yy)
 ifneq ($(CONFIG_SYS_MALLOC_F_LEN),)
 subtract_sys_malloc_f_len = space=$$(($${space} - $(CONFIG_SYS_MALLOC_F_LEN)))
 else