drm/bridge/synopsys: Add MIPI DSI2 host controller bridge

Add a Synopsys Designware MIPI DSI host DRM bridge driver for their
DSI2 host controller, based on the Rockchip version from the driver
rockchip/dw-mipi-dsi2.c in their vendor-kernel with phy & bridge APIs.

While the driver is heavily modelled after the previous IP, the register
set of this DSI2 controller is completely different and there are also
additional properties like the variable-width phy interface.

Tested-by: Daniel Semkowicz <dse@thaumatec.com>
Tested-by: Dmitry Yashin <dmt.yashin@gmail.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Heiko Stuebner <heiko.stuebner@cherry.de>
Reviewed-by: Andy Yan <andy.yan@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20241209231021.2180582-2-heiko@sntech.de