drm/i915: Indent GuC/WOPCM documentation sections

Indent GuC/WOPCM documentation correctly to reside under
"Memory Management and Command Submission" section to avoid
it escaping to the upper level navigation.

Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190830085849.12519-2-joonas.lahtinen@linux.intel.com