commit ea96bc629cbd52be98b2967a4b4f72e91dfc3ee4 doesn't match the patch
submitted by Laszlo to qemu-devel. We reuse pc_q35_2_4_machine_options()
inside pc_q35_2_3_machine_options(), so we need to undo the no_floppy
change in pc_q35_2_3_machine_options().
(This discrepancy was due to a bad merge.)
This restores the previous behavior where all the 2.3 and older machines
had no_floppy=0.