drm/xe/vf: Setup VRAM based on received config data

VF drivers will obtain VRAM configuration from the GuC as part of
the VF self config. Use that configuration instead of trying to
read inaccessible registers.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240530133527.1328-6-michal.wajdeczko@intel.com