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