drm/i915/display: use to_intel_uncore() to avoid i915_drv.h

drm/i915/display: use to_intel_uncore() to avoid i915_drv.h

A number of places that include i915_drv.h only need it to get from
display to i915 to uncore. We have to_intel_uncore() for that, use it to
avoid the i915_drv.h include.

v2: Rebase

Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Michał Grzelak <michal.grzelak@intel.com>
Link: https://patch.msgid.link/44a5d526a097ab9276e60162263fa8cd23325ce7.1766406794.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>