drm/msm/dpu: Fix some kernel-doc comments

Make the description of @init to @p in dpu_encoder_phys_wb_init()
and remove @wb_roi in dpu_encoder_phys_wb_setup_fb() to clear the below
warnings:

drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_wb.c:139: warning: Excess function parameter 'wb_roi' description in 'dpu_encoder_phys_wb_setup_fb'
drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_wb.c:699: warning: Function parameter or member 'p' not described in 'dpu_encoder_phys_wb_init'
drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_wb.c:699: warning: Excess function parameter 'init' description in 'dpu_encoder_phys_wb_init'

Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=3067


Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Fixes: d7d0e73f ("drm/msm/dpu: introduce the dpu_encoder_phys_* for writeback")
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/511605/
Link: https://lore.kernel.org/r/20221115014902.45240-1-yang.lee@linux.alibaba.com


Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>