exynos/dsim: add DT bindings

The patch adds DT bindings for Exynos DSI Master. DSIM follows rules
for DSI bus host bindings [1].
Properties describes its resources: memory, interrupt, clocks,
phy, regulators, frequencies of clocks and video interfaces.

[1]: Documentation/devicetree/bindings/mipi/dsi/mipi-dsi-bus.txt

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>