Link to libOpenCL unconditionally when building OpenCL backend

We only build the OpenCL backend if libOpenCL has been extracted as a
prebuilt library in vendor/google_devices, so relax the check and
assume that libOpenCL is available for linking.

Change-Id: I68cd756fabbc87f5e030a68cf7981a2a53ccb54d
(cherry picked from commit cac505918937a8396f9bca16751016b3a76762d0)

Android.mk

@@ -456,12 +456,8 @@ LOCAL_SHARED_LIBRARIES := \
         android.hidl.memory@1.0
 
 ifeq ($(ARMNN_COMPUTE_CL_ENABLED),1)
-ifeq (,$(realpath $(TOPDIR)vendor/arm/mali/valhall/Android.bp))
-    LOCAL_SHARED_LIBRARIES += libGLES_mali
-else
     LOCAL_SHARED_LIBRARIES += libOpenCL
 endif
-endif
 
 include $(BUILD_EXECUTABLE)
 endif