drm/msm/dsi: don't dump registers past the mapped region

drm/msm/dsi: don't dump registers past the mapped region

On DSI 6G platforms the IO address space is internally adjusted by
io_offset. Later this adjusted address might be used for memory dumping.
However the size that is used for memory dumping isn't adjusted to
account for the io_offset, leading to the potential access to the
unmapped region. Lower ctrl_size by the io_offset value to prevent
access past the mapped area.

 msm_disp_snapshot_add_block+0x1d4/0x3c8 [msm] (P)
 msm_dsi_host_snapshot+0x4c/0x78 [msm]
 msm_dsi_snapshot+0x28/0x50 [msm]
 msm_disp_snapshot_capture_state+0x74/0x140 [msm]
 msm_disp_snapshot_state_sync+0x60/0x90 [msm]
 _msm_disp_snapshot_work+0x30/0x90 [msm]
 kthread_worker_fn+0xdc/0x460
 kthread+0x120/0x140

Fixes: bac2c6a62ed9 ("drm/msm: get rid of msm_iomap_size")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/721747/
Link: https://lore.kernel.org/r/20260428-msm-fix-dsi-dump-v1-1-5d4cb5ccfac7@oss.qualcomm.com