ARM: dts: exynos: Enable HDMI for Arndale Octa board

* GPIO for HDMI hot plug detect
  GPX3_7 is used. The HPD awareness is done when the GPIO is active high.

* Enable HDMI block in Exynos5420
  HDMI VDD and PLL consume 1.0V LDO6 (PVDD_ANAIP_1V0) and HDMI oscillator
  requires 1.8V LDO7 (PVDD_ANAIP_1V8).

* Support HDMI display data channel
  I2C #2 is assigned for the HDMI DDC. It enables the EDID access.

Cc: Kukjin Kim <kgene@kernel.org>
Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-samsung-soc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Milo Kim <woogyom.kim@gmail.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>