floppy: cancel any pending fd_timeouts before adding a new one

In commit 070ad7e7 ("floppy: convert to delayed work and
single-thread wq") the 'fd_timeout' timer was converted to a delayed
work.  However, the "del_timer(&fd_timeout)" was lost in the process,
and any previous pending timeouts would stay active when we then
re-queued the timeout.

This resulted in the floppy probe sequence having a (stale) 20s timeout
rather than the intended 3s timeout, and thus made booting with the
floppy driver (but no actual floppy controller) take much longer than it
should.

Of course, there's little reason for most people to compile the floppy
driver into the kernel at all, which is why most people never noticed.

Canceling the delayed work where we used to do the del_timer() fixes the
issue, and makes the floppy probing use the proper new timeout instead.
The three second timeout is still very wasteful, but better than the 20s
one.

Reported-and-tested-by: Andi Kleen <ak@linux.intel.com>
Reported-and-tested-by: Calvin Walton <calvin.walton@kepstin.ca>
Cc: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>