fixup: cpu: x64: brgemm: fix hidden operator==

c++20 introduced new mechanics of comparison operators and now certain
scenarios require both operator== and operator!= to be defined so that
the operation would be equivalent for a X b and b X a.

src/cpu/x64/brgemm/jit_brgemm_amx_uker.cpp

@@ -263,6 +263,9 @@ struct jit_brgemm_amx_uker_base_t : public jit_generator {
         virtual bool operator==(const dim_iteration_t &rhs) const {
             return blocks == rhs.blocks;
         }
+        virtual bool operator!=(const dim_iteration_t &rhs) const {
+            return !operator==(rhs);
+        }
 
         size_t pos(size_t b) const {
             assert(b < blocks.size());
@@ -318,6 +321,9 @@ struct jit_brgemm_amx_uker_base_t : public jit_generator {
                     && zp_comp_pad_a_shift == rhs.zp_comp_pad_a_shift;
             return res;
         }
+        bool operator!=(const dim_iteration_t &_rhs) const override {
+            return !operator==(_rhs);
+        }
     };
 
     struct bs_iteration_t {