drm/msm/dpu: enable virtual planes by default

drm/msm/dpu: enable virtual planes by default

Turn on the switch and use virtual planes by default, enhancing
utilisation of the display pipelines. It is still possible to use legacy
implementation by using `msm.dpu_use_virtual_planes=false` kernel boot
parameter.

Acked-by: Neil Armstrong <neil.armstrong@linaro.org>
Acked-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Tested-by: Val Packett <val@packett.cool> # x1e80100-dell-latitude-7455,
Patchwork: https://patchwork.freedesktop.org/patch/707437/
Link: https://lore.kernel.org/r/20260226-dpu-enable-virt-planes-v2-1-87971236fe86@oss.qualcomm.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>