drm/i915: remove struct_member macro

Since it is used only to get type of member it can be replaced
with typeof_member.

Signed-off-by: Andrzej Hajda <andrzej.hajda@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221209121459.3496148-1-andrzej.hajda@intel.com