COMPMID-2177 Fix clang warnings

Change-Id: I78039db8c58d7b14a042c41e54c25fb9cb509bf7
Signed-off-by: Michalis Spyrou <michalis.spyrou@arm.com>
Reviewed-on: https://review.mlplatform.org/c/1092
Reviewed-by: VidhyaSudhan Loganathan <vidhyasudhan.loganathan@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
diff --git a/arm_compute/runtime/HOG.h b/arm_compute/runtime/HOG.h
index 70d8034..3dc2f32 100644
--- a/arm_compute/runtime/HOG.h
+++ b/arm_compute/runtime/HOG.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, 2017 ARM Limited.
+ * Copyright (c) 2016-2019 ARM Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -49,8 +49,8 @@
     float         *descriptor() const override;
 
 private:
-    HOGInfo                  _info;
-    std::unique_ptr<float[]> _descriptor;
+    HOGInfo                    _info;
+    mutable std::vector<float> _descriptor;
 };
 }
 #endif /* __ARM_COMPUTE_HOG_H__ */