m68k: mac - Add a new entry in mac_model to identify the floppy controller type.

This patch adds a field "floppy_type" which can take the following values:

MAC_FLOPPY_IWM for an IWM based mac
MAC_FLOPPY_SWIM_ADDR1 for a SWIM based mac with controller at VIA1 + 0x1E000
MAC_FLOPPY_SWIM_ADDR2 for a SWIM based mac with controller at VIA1 + 0x16000
MAC_FLOPPY_IOP for an IOP based mac
MAC_FLOPPY_AV for an AV based mac

Signed-off-by: Laurent Vivier <Laurent@lvivier.info>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>