drm/i915: Use the fdinfo helper

Use the common fdinfo helper for printing the basics. Remove now unused
client id allocation code.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Rob Clark <robdclark@chromium.org>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230605123224.373633-1-tvrtko.ursulin@linux.intel.com