drm/i915/uncore: add to_intel_uncore() and use it

Add to_intel_uncore() function to avoid the inclusion of i915_drv.h from
intel_de.h. This reveals a number of implicit dependencies on i915_drv.h
that need to be added.

For now, to_intel_uncore() can be an inline function, with all the
includes in compat intel_uncore.h, as long as i915_drv.h isn't
included. The implicit dependencies on i915_drv.h is a problem in
display code, but the same is not true for xe_device.h etc.

Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/377e2b400d126776224fc49874ed9cb03ac3123c.1732104170.git.jani.nikula@intel.com