drm/i915: Fix memory leaks in scatterlist

This patch fixes memory leaks on error escapes in i915_scatterlist.c

Fixes: c3bfba9a

 ("drm/i915: Check for integer truncation on scatterlist creation")
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Matt Atwood <matthew.s.atwood@intel.com>
Reviewed-by: Harish Chegondi <harish.chegondi@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230201232801.123684-1-matthew.s.atwood@intel.com