drm/sprd: add Unisoc's drm mipi dsi&dphy driver

Adds dsi host controller support for the Unisoc's display subsystem.
Adds dsi phy support for the Unisoc's display subsystem.
Only MIPI DSI Displays supported, DP/TV/HMDI will be support
in the feature.

v1:
- Remove dphy and dsi graph binding, merge the dphy driver into the dsi.

v2:
- Use drm_xxx to replace all DRM_XXX.
- Use kzalloc to replace devm_kzalloc for sprd_dsi structure init.

v4:
- Use drmm_helpers to allocate encoder.
- Move allocate encoder and connector to bind function.

v5:
- Drop the dsi ip file prefix.
- Fix the checkpatch warnings.
- Add Signed-off-by for dsi&dphy patch.
- Use the mode_flags of mipi_dsi_device to setup crtc DPI and EDPI mode.

v6:
- Redesign the way to access the dsi register.
- Reduce the dsi_context member variables.

v7:
- Fix codeing style issue by checkpatch.
- Drop the pll registers structure define.
- Use bridge API instead of drm panel API.
- Register mipi_dsi_host on probe phase;
- Remove some unused function.

v8:
- Fix missing signed-off-by.
- Move component_add to dsi_host.attach callback.

Cc: Orson Zhai <orsonzhai@gmail.com>
Cc: Chunyan Zhang <zhang.lyra@gmail.com>
Signed-off-by: Kevin Tang <kevin.tang@unisoc.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211207142717.30296-7-kevin3.tang@gmail.com