meson: test for CONFIG_TCG in config_all

meson: test for CONFIG_TCG in config_all

CONFIG_TCG is not included in *-config-devices.h, so the test is
always failing.

Fixes: 74884cb1a6d ("qtest/meson.build: check CONFIG_TCG for boot-serial-test in qtests_ppc", 2022-03-14)
Fixes: 44d827ea69e ("qtest/meson.build: check CONFIG_TCG for prom-env-test in qtests_ppc", 2022-03-14)
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20230830095347.132485-1-pbonzini@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>