ARM: dts: exynos: use generic node name for LPDDR3 timings in Odroid

The node names should have generic name, so use "timings" for LPDDR3
timings.  This will also be required by dtschema.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20220201114749.88500-1-krzysztof.kozlowski@canonical.com