drm/exynos: add support for apb mapped phys in hdmi driver

Previous SoCs have hdmi phys which are accessible through
dedicated i2c lines. Newer SoCs have Apb mapped hdmi phys.
Hdmi driver is modified to support apb mapped phys.

Signed-off-by: Rahul Sharma <Rahul.Sharma@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>