Add more headers to the header test list:

* i915_drv.h
* i915_params.h
* i915_reg.h
* intel_drv.h
* intel_uncore.h

Happily they already are self-contained, but keep them that way.
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/f660e7e1258b81d50475fa73f610eb3312c83424.1556540889.git.jani.nikula@intel.com