ARM: dts: s5pv210: Add DMC nodes

This commit adds DMC (Dynamic Memory Controller) nodes, which are needed
by S5Pv210 cpufreq driver to work.

Signed-off-by: Paweł Chmiel <pawel.mikolaj.chmiel@gmail.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>