COMPMID-3069 Fix bug on QASYMM8_SIGNED GEMMLowp CL kernel

Solves a bug involving a call to vstore4 with wrong argument types in gemmlowp.cl. This bug was introduced in COMPMID-2967.

Signed-off-by: Luca Foschiani <luca.foschiani@arm.com>
Change-Id: If78b01dded51d026737bac829b4aee441088fab5
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/2944
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Sang-Hoon Park <sang-hoon.park@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
diff --git a/src/core/CL/cl_kernels/gemmlowp.cl b/src/core/CL/cl_kernels/gemmlowp.cl
index 7f28286..71de1d4 100644
--- a/src/core/CL/cl_kernels/gemmlowp.cl
+++ b/src/core/CL/cl_kernels/gemmlowp.cl
@@ -2132,7 +2132,7 @@
 #endif // defined(MAX_BOUND)
 
     // Store the result
-    vstore4(res, 0, dst_addr);
+    vstore4(res, 0, (__global OUTPUT_DATA_TYPE *)dst_addr);
 }
 #endif // defined(RESULT_OFFSET) && defined(RESULT_MULT_INT) && defined(RESULT_SHIFT)