hw: Remove device_phases_reset()

hw: Remove device_phases_reset()

Currently we have transitional machinery between legacy reset
and three phase reset that works in two directions:
 * if you invoke three phase reset on a device which has set
   the DeviceClass::legacy_reset method, we detect this in
   device_get_transitional_reset() and arrange that we call
   the legacy_reset method during the hold phase of reset
 * if you invoke legacy reset on a device which implements
   three phase reset, the default legacy_reset method is
   device_phases_reset(), which does a three-phase reset
   of the device

However, we have now eliminated all the places which could invoke
legacy reset on a device, which means that the function
device_phases_reset() is never called -- it serves only as the value
of DeviceClass::legacy_reset that indicates that the subclass never
overrode the legacy reset method.  So we can delete it, and instead
check for legacy_reset != NULL.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20240830145812.1967042-10-peter.maydell@linaro.org