drm/i915: Fixup kerneldoc code snippets in intel_uncore.c

We need :: before, blank lines around and indentation with 4 _additional_
spaces to make it work. Also, don't use @param in code snippets, it results
in confusion.

Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1468612088-9721-8-git-send-email-daniel.vetter@ffwll.ch