arm64: dts: qcom: add gpu_zap_shader label

arm64: dts: qcom: add gpu_zap_shader label

Patching existing DT nodes based on full path is error prone and
generally not recommended. Follow the pattern introduced in the last
platforms, add gpu_zap_shader label to the ZAP node and use it in the
board files.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Reviewed-by: David Heidelberg <david@ixit.cz>
Link: https://lore.kernel.org/r/20251028-dt-zap-shader-v1-7-7eccb823b986@oss.qualcomm.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>