drm/doc: Switch to sphinx/rst fixed-width quoting

Just fallout from switching from asciidoc to sphinx/rst.

v2: Found more. Also s/\//#/ in the vgpu ascii-art - sphinx treats
those as comments and switch to variable-width, which wreaks the
layout.

v3: Undo some of the hacks, rebasing onto latest version of Jani's
series fixed it.

Acked-by: Liviu Dudau <Liviu.Dudau@arm.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index b365440..2555430 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -36,7 +36,7 @@
  * encoder chain.
  *
  * A bridge is always attached to a single &drm_encoder at a time, but can be
- * either connected to it directly, or through an intermediate bridge:
+ * either connected to it directly, or through an intermediate bridge::
  *
  *     encoder ---> bridge B ---> bridge A
  *