fix compilation errors on linux with gcc12

Signed-off-by: Sunita Nadampalli <nadampal@amazon.com>
Change-Id: I21eca31d97d6e2ca8279adb9db65f11540e72689
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/11396
Benchmark: Arm Jenkins <bsgcomp@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Pablo Marquez Tello <pablo.tello@arm.com>
diff --git a/src/core/NEON/kernels/arm_gemm/kernels/a64_ffhybrid_fp32bf16fp32_mmla_6x16/generic.cpp b/src/core/NEON/kernels/arm_gemm/kernels/a64_ffhybrid_fp32bf16fp32_mmla_6x16/generic.cpp
index 0bf0d2a..9ab4aa9 100644
--- a/src/core/NEON/kernels/arm_gemm/kernels/a64_ffhybrid_fp32bf16fp32_mmla_6x16/generic.cpp
+++ b/src/core/NEON/kernels/arm_gemm/kernels/a64_ffhybrid_fp32bf16fp32_mmla_6x16/generic.cpp
@@ -50,8 +50,8 @@
         size_t output_offset = {};
         size_t input_initial_col = {};
         size_t input_offset = {};
-        void *output_ptr;
-        const float *bias;
+        void *output_ptr = nullptr;
+        const float *bias = nullptr;
     } ka;
 
     unsigned long flags=0;