Fix ifdef, its operand is literal variable name

Bug: 173737347
Test: treehugger
Change-Id: Id7bcbb13c69514884c9859e4593569b36f3d86ec
diff --git a/hikey960/device-hikey960.mk b/hikey960/device-hikey960.mk
index e6730a1..b722755 100644
--- a/hikey960/device-hikey960.mk
+++ b/hikey960/device-hikey960.mk
@@ -58,7 +58,7 @@
 			libmalicore.bc \
 			END_USER_LICENCE_AGREEMENT.txt
 
-ifdef $(MALI_RS_DRIVER_AVAILABLE)
+ifdef MALI_RS_DRIVER_AVAILABLE
 PRODUCT_COPY_FILES += \
         $(LOCAL_PATH)/../mali/bifrost/lib/libclcore.bc:vendor/lib/libclcore.bc \
         $(LOCAL_PATH)/../mali/bifrost/lib/libclcore_neon.bc:vendor/lib/libclcore_neon.bc \