drm/xe/pf: Introduce helper functions for use by PF

PF driver will maintain VF's configuration data mostly on the
GT level, but some internal data is located at the device level.

To allow easy access to that data from the GT level functions, and
to minimize code duplications, introduce set of helper functions
and macros for explicit use by the PF driver.

We will use these helpers in upcoming patches.

Reviewed-by: Piotr Piórkowski <piotr.piorkowski@intel.com>
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240410170338.1199-3-michal.wajdeczko@intel.com