drm/xe/pf: Fix documentation formatting

Current formatting of "The VF FLR Flow with GuC" only looks fine,
but it will not render properly when included in htmldocs due to:

  WARNING: Block quote ends without a blank line; unexpected unindent.
  CRITICAL: Missing matching underline for section title overline.

Fix that by adding proper indent and using list markup.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Piotr Piórkowski <piotr.piorkowski@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240828210809.1528-3-michal.wajdeczko@intel.com