drm/i915/dpt: rename struct i915_dpt to intel_dpt

drm/i915/dpt: rename struct i915_dpt to intel_dpt

Rename struct i915_dpt to intel_dpt. This may seem rather inconsistent
considering we just renamed the functions the other way round, but the
intent here is to lift struct intel_dpt to the display parent interface
as the generic opaque type for DPT instead of the very specific struct
i915_address_space.

Reviewed-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Link: https://patch.msgid.link/afb89dcce35c5b0cff2007b58d6ee20fd3200c24.1772030909.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>