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

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

Correct or add kernel-doc comments to eliminate all warnings:

Warning: drivers/gpu/drm/msm/disp/dpu1/dpu_hw_wb.h:24 Cannot find
 identifier on line: *
Warning: drivers/gpu/drm/msm/disp/dpu1/dpu_hw_wb.h:57 struct member
 'setup_roi' not described in 'dpu_hw_wb_ops'
Warning: drivers/gpu/drm/msm/disp/dpu1/dpu_hw_wb.h:75 struct member
 'caps' not described in 'dpu_hw_wb'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/695672/
Link: https://lore.kernel.org/r/20251219184638.1813181-16-rdunlap@infradead.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>