qemu: simplify machine-type check for implicit floppy controller

qemu: simplify machine-type check for implicit floppy controller

Q35 machine types 2.3 and older had an integrated floppy controller.

Support for these machine types was removed by QEMU commit

  commit 86165b499edf8b03bb2d0e926d116c2f12a95bfe
      q35: Remove old machine versions
  git describe: v2.5.0-1530-g86165b499e contains: v2.6.0-rc0~76^2~4

In libvirt, we have bumped the minimum QEMU version to 2.11:

  commit b4cbdbe90bbf85eaf687f532d5a52a11e664b781
    qemu: Formally deprecate support for qemu < 2.11
  git describe: v7.3.0-13-gb4cbdbe90b contains: v7.4.0-rc1~300

Since this QEMU version only supports Q35 machine versions 2.4+,
remove the code dealing with older ones.

Signed-off-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>