drm: bridge: analogix/dp: split exynos dp driver to bridge directory

Split the dp core driver from exynos directory to bridge directory,
and rename the core driver to analogix_dp_*, rename the platform
code to exynos_dp.

Beside the new analogix_dp driver would export six hooks.
"analogix_dp_bind()" and "analogix_dp_unbind()"
"analogix_dp_suspned()" and "analogix_dp_resume()"
"analogix_dp_detect()" and "analogix_dp_get_modes()"

The bind/unbind symbols is used for analogix platform driver to connect
with analogix_dp core driver. And the detect/get_modes is used for analogix
platform driver to init the connector.

They reason why connector need register in helper driver is rockchip drm
haven't implement the atomic API, but Exynos drm have implement it, so
there would need two different connector helper functions, that's why we
leave the connector register in helper driver.

Acked-by: Inki Dae <inki.dae@samsung.com>
Tested-by: Caesar Wang <wxt@rock-chips.com>
Tested-by: Douglas Anderson <dianders@chromium.org>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Yakir Yang <ykk@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>