memory: tegra20-emc: Continue probing if timings are missing in device-tree

memory: tegra20-emc: Continue probing if timings are missing in device-tree

EMC driver will become mandatory after turning it into interconnect
provider because interconnect users, like display controller driver, will
fail to probe using newer device-trees that have interconnect properties.
Thus make EMC driver to probe even if timings are missing in device-tree.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Link: https://lore.kernel.org/r/20201104164923.21238-35-digetx@gmail.com
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>