DSI host registration, attach and detach operations are quite
different for the component and bridge-based DRM drivers.

Supporting generic bridge driver to use both component and bridge
based DRM drivers can be tricky and would require additional host
related operation hooks.

Add host operation hooks for registering and unregistering Exynos
and generic drivers, where Exynos hooks are used in existing Exynos
component based DRM drivers and generic hooks are used in i.MX8M
bridge based DRM drivers.

Add host attach and detach operation hooks for Exynos component
DRM drivers and those get invoked while DSI core host attach and
detach gets called.

Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>