drm/i915: Remove unused intel_huc_suspend

intel_huc_suspend() was added in 2022 by
commit 27536e03 ("drm/i915/huc: track delayed HuC load with a
fence")
but hasn't been used.

Remove it.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Signed-off-by: Tvrtko Ursulin <tursulin@igalia.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241227113754.25871-2-tursulin@igalia.com