COMPMID-2796: Add support for QASYMM8_SIGNED in NEActivationLayer and NEPReluLayer

Change-Id: I089fd19a6beab7779d690bc9ace327f661c2753d
Signed-off-by: Michalis Spyrou <michalis.spyrou@arm.com>
Reviewed-on: https://review.mlplatform.org/c/2407
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Michele Di Giorgio <michele.digiorgio@arm.com>
diff --git a/arm_compute/core/QuantizationInfo.h b/arm_compute/core/QuantizationInfo.h
index 7a6fe42..06ba665 100644
--- a/arm_compute/core/QuantizationInfo.h
+++ b/arm_compute/core/QuantizationInfo.h
@@ -33,9 +33,10 @@
 
 namespace arm_compute
 {
-using qasymm8_t  = uint8_t;  /**< 8 bit quantized asymmetric scalar value */
-using qsymm16_t  = int16_t;  /**< 16 bit quantized symmetric scalar value */
-using qasymm16_t = uint16_t; /**< 16 bit quantized asymmetric scalar value */
+using qasymm8_signed_t = int8_t;   /**< 8 bit signed quantized asymmetric scalar value */
+using qasymm8_t        = uint8_t;  /**< 8 bit quantized asymmetric scalar value */
+using qsymm16_t        = int16_t;  /**< 16 bit quantized symmetric scalar value */
+using qasymm16_t       = uint16_t; /**< 16 bit quantized asymmetric scalar value */
 
 /** Quantization info when assuming per layer quantization */
 struct UniformQuantizationInfo