arm: On arm the virtual console is PL011-based ttyAMA0.

Confusingly real ARM hardware can have either PC-like 8250 devices,
which the Linux kernel calls /dev/ttyS0, or ARM-only PL011-based
/dev/ttyAMA0.

qemu can emulate either, but the default for `-M virt' is the PL011
so /dev/ttyAMA0.

Change the warning message so it uses ttyAMA0 instead.

virt-install

@@ -358,10 +358,13 @@ def _show_nographics_warnings(options, guest):
         return
 
     serial_arg = "console=ttyS0"
+    serial_arm_arg = "console=ttyAMA0"
     virtio_arg = "console=hvc0"
     console_type = None
     if guest.conn.is_test() or guest.conn.is_qemu():
         console_type = serial_arg
+        if guest.os.arch.startswith("arm") or guest.os.arch == "aarch64":
+            console_type = serial_arm_arg
         if guest.get_devices("console")[0].target_type == "virtio":
             console_type = virtio_arg