drm/msm/dpu: dpu_hw_merge3d.h: fix all kernel-doc warnings

Delete one "empty" kernel-doc line to eliminate a warning:

Warning: drivers/gpu/drm/msm/disp/dpu1/dpu_hw_merge3d.h:14 Cannot find
 identifier on line: *

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/695673/
Link: https://lore.kernel.org/r/20251219184638.1813181-11-rdunlap@infradead.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>