arm64: dts: exynos: Add reserved memory for pstore on E850-96

arm64: dts: exynos: Add reserved memory for pstore on E850-96

Reserve a 2 MiB memory region to record kmsg dumps, console, ftrace and
userspace messages. The implemented memory split allows capturing and
reading corresponding ring buffers:
  * dmesg: 6 dumps, 128 KiB each
  * console: 128 KiB
  * ftrace: 128 KiB for each of 8 CPUs (1 MiB total)
  * userspace messages: 128 KiB

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Link: https://lore.kernel.org/r/20231008033633.21304-1-semen.protsenko@linaro.org
[krzysztof: move the node to alphabetically sorted position]
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>