Samsung MIPI DSIM controller is common DSI IP that can be used in various
SoCs like Exynos, i.MX8M Mini/Nano.

In order to access this DSI controller between various platform SoCs,
the ideal way to incorporate this in the drm stack is via the drm bridge
driver.

This patch is trying to differentiate platform-specific and bridge driver
code and keep maintaining the exynos_drm_dsi.c code as platform-specific
glue code and samsung-dsim.c as a common bridge driver code.

- Exynos specific glue code is exynos specific te_irq, host_attach, and
  detach code along with conventional component_ops.

- Samsung DSIM is a bridge driver which is common across all platforms and
  the respective platform-specific glue will initialize at the end of the
  probe. The platform-specific operations and other glue calls will invoke
  on associate code areas.

[mszyprow]
* reworked driver initialization using the same approach as in
  drivers/gpu/drm/{exynos/exynos_dp.c, bridge/analogix/analogix_dp_core.c},
  removed weak functions, moved exynos_dsi_driver back to exynos_drm_dsi.c
  and restored integration with exynos_drm custom intialization

v4:
* include Inki Dae in MAINTAINERS
* remove dsi_driver probe in exynos_drm_drv to support multi-arch build

v3:
* restore gpio related fixes
* restore proper bridge chain
* rework initialization issue
* fix header includes in proper way

v2:
* fixed exynos dsi driver conversion (Marek Szyprowski)
* updated commit message
* updated MAINTAINERS file

v1:
* don't maintain component_ops in bridge driver
* don't maintain platform glue code in bridge driver
* add platform-specific glue code and make a common bridge

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>