ARM: dts: exynos: Extend the eMMC node on Arndale Octa

Describe properly the MMC0 node (with attached embedded MMC memory) on
Arndale Octa by:
1. Adding the regulator for host interface (although it still has to be
   "always-on" so the board with Linaro U-Boot will boot properly);
2. Using "non-removable" instead of "broken-cd" property, because eMMC
   is embedded into the board;
3. Adding support for HS200 v1.8 to indicate such support in host
   controller although this has no practical effect (embedded memory does
   not support it).

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>