drm/i915/sdvo: Tidy up commentary

Drop the kerneldoc markup from the non-kerneldoc comments and convert
the multi-line comments to the canonical format.

drivers/gpu/drm/i915/intel_sdvo.c:223: warning: Function parameter or member 'intel_sdvo' not described in 'intel_sdvo_write_sdvox'
drivers/gpu/drm/i915/intel_sdvo.c:223: warning: Function parameter or member 'val' not described in 'intel_sdvo_write_sdvox'
drivers/gpu/drm/i915/intel_sdvo.c:653: warning: Function parameter or member 'intel_sdvo' not described in 'intel_sdvo_get_trained_inputs'
drivers/gpu/drm/i915/intel_sdvo.c:653: warning: Function parameter or member 'input_1' not described in 'intel_sdvo_get_trained_inputs'
drivers/gpu/drm/i915/intel_sdvo.c:653: warning: Function parameter or member 'input_2' not described in 'intel_sdvo_get_trained_inputs'
drivers/gpu/drm/i915/intel_sdvo.c:2311: warning: Function parameter or member 'dev_priv' not described in 'intel_sdvo_select_ddc_bus'
drivers/gpu/drm/i915/intel_sdvo.c:2311: warning: Function parameter or member 'sdvo' not described in 'intel_sdvo_select_ddc_bus'

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180214090905.4747-1-chris@chris-wilson.co.uk