drm/xe/vf: Read VF configuration prior to GGTT initialization

Each VF will be assigned with only a limited range of the GGTT
address space. Make sure that VF driver will read its own GGTT
configuration before starting any GGTT initialization.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240524113714.932-2-michal.wajdeczko@intel.com