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

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

flavours/linux/conf-notes.txt

@@ -29,6 +29,6 @@ or via command line, e.g.:
 
 You can also run generated qemu images with a command:
 
-    $ runqemu qemux86-64 qemuparams="-nographic" oniro-image-base wic ovmf slirp
+    $ runqemu qemux86-64 oniro-image-base wic ovmf slirp nographic
 
 Then log in as 'oniro' user with 'oniro' as a password.