Don't pass a NULL pointer in to SYS_signalfd in qemu_signalfd_available():
this isn't valid and Valgrind complains about it.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: NAndrzej Zaborowski <andrew.zaborowski@intel.com>