* ggml: fix gradient allocation logic * gradient allocation in ggml_build_backward_expand * fixup * fix test-backend-ops grad * suggestions by slaren * fix test1.c * fix legacy opt API * fix test-grad0 * remove keep arg
* ggml: fix gradient allocation logic * gradient allocation in ggml_build_backward_expand * fixup * fix test-backend-ops grad * suggestions by slaren * fix test1.c * fix legacy opt API * fix test-grad0 * remove keep arg