testimage: Allow testing on QEMU machines with a single serial port
commmit
6cde67d0a84 enables the use of qemurunner on machines that
only have a single serial port, but still sets the default value
as serial_ports=2 if not provided.
The testimage class does not call qemurunner with a serial_ports
argument, hence always defaulting to two.
Pass the serial_ports argument from the testimage class to allow
tests to run on QEMU machines with a single serial port.
Signed-off-by: Alejandro Hernandez Samaniego <alejandro@enedino.org>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
