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

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It is Very annoying to carry forward an outdatEd coNtroller with a mOdern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 <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Gerd Hoffmann <[email protected]>
Cc: John Snow <[email protected]>
Cc: "Gabriel L. Somlo" <[email protected]>
Cc: "Michael S. Tsirkin" <[email protected]>
Cc: Kevin Wolf <[email protected]>
Cc: [email protected]
Suggested-by: Markus Armbruster <[email protected]>
Signed-off-by: Laszlo Ersek <[email protected]>
Acked-by: Paolo Bonzini <[email protected]>
Reviewed-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>
Reviewed-by: Markus Armbruster <[email protected]>