IVGCVSW-798 Add Softmax NEON support for QASYMM8

Change-Id: I4f2cca52caf210fdb7d6bb7e9436ac51cb5088b4
Reviewed-on: https://eu-gerrit-1.euhpc.arm.com/112398
Reviewed-by: Anthony Barbier <anthony.barbier@arm.com>
Tested-by: Jenkins <bsgcomp@arm.com>
diff --git a/arm_compute/core/Error.h b/arm_compute/core/Error.h
index 97dbba3..56c7ccd 100644
--- a/arm_compute/core/Error.h
+++ b/arm_compute/core/Error.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, 2017 ARM Limited.
+ * Copyright (c) 2016-2018 ARM Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -86,7 +86,7 @@
         return _error_description;
     }
     /** Throws a runtime exception in case it contains a valid error status */
-    void throw_if_error()
+    void throw_if_error() const
     {
         if(!bool(*this))
         {
@@ -96,7 +96,7 @@
 
 private:
     /** Internal throwing function */
-    [[noreturn]] void internal_throw_on_error();
+    [[noreturn]] void internal_throw_on_error() const;
 
 private:
     ErrorCode   _code;