meson: Rename softmmu_mods -> system_mods
See commit de6cd7599b ("meson: Replace softmmu_ss -> system_ss")
for rationale.
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20231004090629.37473-12-philmd@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>