metal : disable support for MUL_MAT F32 x F16

ggml-metal.m

@@ -668,7 +668,8 @@ static bool ggml_metal_supports_op(const struct ggml_metal_context * ctx, const
             return true;
         case GGML_OP_MUL_MAT:
         case GGML_OP_MUL_MAT_ID:
-            return ctx->support_simdgroup_reduction;
+            return ctx->support_simdgroup_reduction &&
+                (op->src[0]->type != GGML_TYPE_F32 || op->src[1]->type == GGML_TYPE_F32);
         case GGML_OP_CPY:
         case GGML_OP_DUP:
         case GGML_OP_CONT: