drm/doc: Polish for drm_mode_parse_command_line_for_connector

Quoting the module option format looks soo much nicer, and avoids
sphinx spewing errors about markup issues.

v2: Fix typo in commit message (Thierry).
Reviewed-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180219225356.24996-4-daniel.vetter@ffwll.ch

drivers/gpu/drm/drm_modes.c

@@ -1346,9 +1346,9 @@ EXPORT_SYMBOL(drm_mode_connector_list_update);
  * modeline in fb_mode_option will be parsed instead.
  *
  * This uses the same parameters as the fb modedb.c, except for an extra
- * force-enable, force-enable-digital and force-disable bit at the end:
+ * force-enable, force-enable-digital and force-disable bit at the end::
  *
- * <xres>x<yres>[M][R][-<bpp>][@<refresh>][i][m][eDd]
+ *	<xres>x<yres>[M][R][-<bpp>][@<refresh>][i][m][eDd]
  *
  * The intermediate drm_cmdline_mode structure is required to store additional
  * options from the command line modline like the force-enable/disable flag.