Documentation/i915: remove kernel-doc for DMC wakelocks

The function descriptions are optional and have not yet been added to
the DMC wakelock code, so we shouldn't try to use it.  Since this is a
regression, remove the kernel-doc entry for DMC wakelocks for now.
The proper documentation will be added in a future patch.

Fixes: 765425f5 ("drm/i915/display: add support for DMC wakelocks")
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240510090502.667556-1-luciano.coelho@intel.com