drm/xe/pf: Add functions to save and restore VF GuC state

To successfully migrate a VM with attached GPU VF we also need to
migrate VF's GuC state. Add necessary functions that interacts with
GuC to save and restore a VF GuC state. We will start using them in
upcoming patches.

Since VF migration requires many more changes in the driver, enable
those functions only under debug config.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Tomasz Lis <tomasz.lis@intel.com>
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240913120013.1924-1-michal.wajdeczko@intel.com