IVGCVSW-2603 The macros ARMCOMPUTECL_ENABLED and ARMCOMPUTENEON_ENABLED
no longer work

 * Added two master variables ARMNN_COMPUTE_CL_ENABLED and ARMNN_COMPUTE_NEON_ENABLED
   to android-nn-driver/Android.mk to easily control backend support
 * Setting either of those two new variables then properly sets the
   corresponding build macro
 * If a specific backend gets disabled, the corresponding source files
   will be excluded from the build
 * Unified the usage of the pre-compile macros

!android-nn-driver:613

Change-Id: I582ff73493b70ba9e22ca2e38d875a0f19566c8a
Signed-off-by: Matteo Martincigh <matteo.martincigh@arm.com>
diff --git a/src/backends/aclCommon/BaseMemoryManager.cpp b/src/backends/aclCommon/BaseMemoryManager.cpp
index f564dc6..7c06ec5 100644
--- a/src/backends/aclCommon/BaseMemoryManager.cpp
+++ b/src/backends/aclCommon/BaseMemoryManager.cpp
@@ -89,7 +89,7 @@
 }
 #endif
 
-#ifdef ARMCOMPUTENEON_ENABLED
+#if defined(ARMCOMPUTENEON_ENABLED)
 std::shared_ptr<arm_compute::IMemoryGroup>
 NeonMemoryManager::CreateMemoryGroup(const std::shared_ptr<arm_compute::MemoryManagerOnDemand>& memoryManager)
 {
@@ -97,7 +97,7 @@
 }
 #endif
 
-#ifdef ARMCOMPUTECL_ENABLED
+#if defined(ARMCOMPUTECL_ENABLED)
 std::shared_ptr<arm_compute::IMemoryGroup>
 ClMemoryManager::CreateMemoryGroup(const std::shared_ptr<arm_compute::MemoryManagerOnDemand>& memoryManager)
 {