drm/panel: Changes for v4.6-rc1

This contains a refactoring of parts of the DSI core to allow creating
DSI devices from non-DSI control busses (i.e. I2C, SPI, ...).

Other than that there's support for a couple of new panels as well as
a few cleanup patches.

* tag 'drm/panel/for-4.6-rc1' of http://anongit.freedesktop.org/git/tegra/linux:
  drm/bridge: Make (pre/post) enable/disable callbacks optional
  drm/panel: simple: Add URT UMSH-8596MD-xT panels support
  dt-bindings: Add URT UMSH-8596MD-xT panel bindings
  of: Add United Radiant Technology Corporation vendor prefix
  drm/panel: simple: Support for LG lp120up1 panel
  dt-bindings: Add LG lp120up1 panel bindings
  drm/panel: simple: Fix g121x1_l03 hsync/vsync polarity
  drm/dsi: Get DSI host by DT device node
  drm/dsi: Add routine to unregister a DSI device
  drm/dsi: Try to match non-DT DSI devices
  drm/dsi: Use mipi_dsi_device_register_full() for DSI device creation
  drm/dsi: Check for CONFIG_OF when defining of_mipi_dsi_device_add()