drm/i915: use IOMEM_ERR_PTR() directly

Use IOMEM_ERR_PTR() instead of self defined IO_ERR_PTR().

Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220503144937.679424-1-tvrtko.ursulin@linux.intel.com