drm/docs: Fix usage stats typos

Fix a couple missing ':'s.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230524155956.382440-2-robdclark@gmail.com

Documentation/gpu/drm-usage-stats.rst

@@ -105,7 +105,7 @@ object belong to this client, in the respective memory region.
 Default unit shall be bytes with optional unit specifiers of 'KiB' or 'MiB'
 indicating kibi- or mebi-bytes.
 
-- drm-cycles-<str> <uint>
+- drm-cycles-<str>: <uint>
 
 Engine identifier string must be the same as the one specified in the
 drm-engine-<str> tag and shall contain the number of busy cycles for the given
@@ -117,7 +117,7 @@ larger value within a reasonable period. Upon observing a value lower than what
 was previously read, userspace is expected to stay with that larger previous
 value until a monotonic update is seen.
 
-- drm-maxfreq-<str> <uint> [Hz|MHz|KHz]
+- drm-maxfreq-<str>: <uint> [Hz|MHz|KHz]
 
 Engine identifier string must be the same as the one specified in the
 drm-engine-<str> tag and shall contain the maximum frequency for the given