arm64: dts: qcom: sm8650: Fix GPU cx_mem size

arm64: dts: qcom: sm8650: Fix GPU cx_mem size

This is doubled compared to previous GPUs. We can't access the new
SW_FUSE_VALUE register without this.

Fixes: db33633b05c0 ("arm64: dts: qcom: sm8650: add GPU nodes")
Signed-off-by: Connor Abbott <cwabbott0@gmail.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Link: https://lore.kernel.org/r/20240426-a750-raytracing-v2-1-562ac9866d63@gmail.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>