Don't consider DW_TAG_inlined_subroutine as interesting

tag_interesting_for_index returns true for DW_TAG_inlined_subroutine
-- but this tag only appears where the function is actually inlined,
which is not interesting for the index.

Acked-By: Tom de Vries <tdevries@suse.de>
Approved-By: Simon Marchi <simark@simark.ca>