Refactor: Remove m_ImportFlags from RefTensorHandle

The import flags for a RefTensorHandle shouldn't be a data member,
as RefTensorHandle can only import from MemorySource::Malloc. Instead,
use m_ImportEnabled to determine what to return from GetImportFlags().

Simplifies the code in Import and CanBeImported.

Signed-off-by: Matthew Bentham <matthew.bentham@arm.com>
Change-Id: Ic629858920f7dd32f99ee27f150b81d8b67144cf
diff --git a/src/backends/reference/RefTensorHandleFactory.cpp b/src/backends/reference/RefTensorHandleFactory.cpp
index ade27dd..da3b798 100644
--- a/src/backends/reference/RefTensorHandleFactory.cpp
+++ b/src/backends/reference/RefTensorHandleFactory.cpp
@@ -48,7 +48,7 @@
     }
     else
     {
-        return std::make_unique<RefTensorHandle>(tensorInfo, m_ImportFlags);
+        return std::make_unique<RefTensorHandle>(tensorInfo);
     }
 }
 
@@ -63,7 +63,7 @@
     }
     else
     {
-        return std::make_unique<RefTensorHandle>(tensorInfo, m_ImportFlags);
+        return std::make_unique<RefTensorHandle>(tensorInfo);
     }
 }
 
@@ -87,4 +87,4 @@
     return m_ImportFlags;
 }
 
-} // namespace armnn
\ No newline at end of file
+} // namespace armnn