In the vmbus code we currently use the legacy functions
qdev_reset_all() and qbus_reset_all().  These perform a recursive
reset, starting from either a qbus or a qdev.  However they do not
permit any of the devices in the tree to use three-phase reset,
because device reset goes through the device_legacy_reset() function
that only calls the single DeviceClass::reset method.

Switch to using the device_cold_reset() and bus_cold_reset()
functions.  These also perform a recursive reset, where first the
children are reset and then finally the parent, but they use the new
(...in 2020...) Resettable mechanism, which supports both the old
style single-reset method and also the new 3-phase reset handling.

This should be a no-behaviour-change commit which just reduces the
use of a deprecated API.

Commit created with:
  sed -i -e 's/qdev_reset_all/device_cold_reset/g;s/qbus_reset_all/bus_cold_reset/g' hw/hyperv/*.c

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>