drm/i915: Move variables to loop context

Lot of the loops over VBT child devices have variables
declared outside the loop but only used inside the loop.
Move the variables to a tighter scope.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230208015508.24824-3-ville.syrjala@linux.intel.com


Reviewed-by: Jani Nikula <jani.nikula@intel.com>