arm64: dts: qcom: msm8996: Revamp reserved memory

Fix a total overlap between zap_shader_region and slpi_region, and rename
all regions to match the naming convention in other Qualcomm SoC device trees.

Signed-off-by: Yassine Oudjana <y.oudjana@protonmail.com>
Tested-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> #db820c
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20210926190555.278589-2-y.oudjana@protonmail.com