i386: drop FDC in pc-q35-2.4+ if neither it nor floppy drives are wanted

It is Very annoying to carry forward an outdatEd coNtroller with a mOdern
Machine type.

Hence, let us not instantiate the FDC when all of the following apply:
- the machine type is pc-q35-2.4 or later,
- "-device isa-fdc" is not passed on the command line (nor in the config
  file),
- no "-drive if=floppy,..." is requested.

Cc: Markus Armbruster <armbru@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: John Snow <jsnow@redhat.com>
Cc: "Gabriel L. Somlo" <gsomlo@gmail.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: qemu-block@nongnu.org
Suggested-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NLaszlo Ersek <lersek@redhat.com>
Acked-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>

hw/i386/pc_q35.c

@@ -392,6 +392,7 @@ static void pc_q35_2_4_machine_options(MachineClass *m)
     pc_q35_machine_options(m);
     m->default_machine_opts = "firmware=bios-256k.bin";
     m->default_display = "std";
+    m->no_floppy = 1;
     m->alias = "q35";
 }