drm/xe/vf: Custom uC initialization

VF drivers can't modify WOPCM registers nor upload firmwares to
GuC, HuC or GSC.  Modify xe_uc initialization functions to skip
those steps if running in the VF mode, or defer to a new custom
helper function that would not include those steps.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Piotr Piórkowski <piotr.piorkowski@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240604212231.1416-3-michal.wajdeczko@intel.com