drm/i915: Use sizeof(variable) instead sizeof(type)

Use sizeof(variable) instead of sizeof(type) in the hopes of
less chance of screwing things up.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221026113906.10551-2-ville.syrjala@linux.intel.com


Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>