drm/msm/dpu: Merge setup_- and enable_tearcheck pingpong callbacks

drm/msm/dpu: Merge setup_- and enable_tearcheck pingpong callbacks

These functions are always called consecutively and are best bundled
together for simplicity, especially when the same structure of callbacks
will be replicated later on the interface block for INTF TE support.
The enable_tearcheck(false) case is now replaced with a more obvious
disable_tearcheck(), encapsulating the original register write with 0.

Suggested-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/534217/
Link: https://lore.kernel.org/r/20230411-dpu-intf-te-v4-20-27ce1a5ab5c6@somainline.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>