fdc: Move floppy geometry guessing back from block.c

fdc: Move floppy geometry guessing back from block.c

Commit 5bbdbb46 moved it to block.c because "other geometry guessing
functions already reside in block.c".  Device-specific functionality
should be kept in device code, not the block layer.  Move it back.

Disk geometry guessing is still in block.c.  To be moved out in a
later patch series.

Bonus: the floppy type used in pc_cmos_init() now obviously matches
the one in the FDrive.  Before, we relied on
bdrv_get_floppy_geometry_hint() picking the same type both in
fd_revalidate() and in pc_cmos_init().

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>