ide: cancel pending callbacks on SRST

The SRST implementation did not keep up with the rest of IDE; it is
possible to perform a weak reset on an IDE device to remove the BSY/DRQ
bits, and then issue writes to the control/device registers which can
cause chaos with the state machine.

Fix that by actually performing a real reset.

Reported-by: Alexander Bulekov <alxndr@bu.edu>
Fixes: https://bugs.launchpad.net/qemu/+bug/1878253
Fixes: https://bugs.launchpad.net/qemu/+bug/1887303
Fixes: https://bugs.launchpad.net/qemu/+bug/1887309


Signed-off-by: John Snow <jsnow@redhat.com>