flavours/linux: Fix runqemu arguments to run without X11

runqemu's nographic option sets qemu argument display to none and this allows to use runqemu script in headless environment (without X11) Using nographic qemuparam doesn't affect display setting and sdl is used which causes Could not initialize SDL(x11 not available) - exiting error

Closes: #794 (closed)

Signed-off-by: Pavel Zhukov pavel.zhukov@huawei.com