drm/msm/dpu: offset HBB values written to DPU by -13

drm/msm/dpu: offset HBB values written to DPU by -13

As in all other places, the Highest Bank Bit value should be programmed
into the hardware with the offset of -13.  Correct the value written
into the register to prevent unpredictable results.

Fixes: 227d4ce0b09e ("drm/msm: Offset MDSS HBB value by 13")
Tested-by: Val Packett <val@packett.cool> # x1e80100-dell-latitude-7455
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/699276/
Link: https://lore.kernel.org/r/20260119-msm-ubwc-fixes-v4-2-0987acc0427f@oss.qualcomm.com