Remove compiler warning: target CPU does not support interworking

Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
diff --git a/cpu/arm1136/config.mk b/cpu/arm1136/config.mk
index e39e774..6ab0dd3 100644
--- a/cpu/arm1136/config.mk
+++ b/cpu/arm1136/config.mk
@@ -31,4 +31,5 @@
 #
 # =========================================================================
 PLATFORM_CPPFLAGS +=$(call cc-option,-mapcs-32,-mabi=apcs-gnu)
+PLATFORM_CPPFLAGS +=$(call cc-option,-mno-thumb-interwork,)
 PLATFORM_RELFLAGS +=$(call cc-option,-mshort-load-bytes,$(call cc-option,-malignment-traps,))