floppy,{ami|ata}flop: Convert to bdops->check_events()

floppy,{ami|ata}flop: Convert to bdops->check_events()

Convert the floppy drivers from ->media_changed() to ->check_events().
Both floppy and ataflop buffer media changed state bit and clear them
on revalidation and will behave correctly with kernel event polling.

I can't tell how amiflop clears its event and it's possible that it
may generate spurious events when polled.

Signed-off-by: Tejun Heo <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Kay Sievers <[email protected]>