drm/i915: fix CRC debugfs setup

We've set up all files, but removed only those for which we have a
pipe. Which leaves the one for pipe C on machines with less than 2
pipes, breaking module reload.

v2: We can't get at the drm device this early (wtf), so just register
all the files and also remove them all again.

Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>