fix symbol migration

kpatch_migrate_included_symbols() is called from
kpatch_reorder_symbols() now, not kpatch_migrate_included_elements().
The difference is the kpatch_reorder_symbols() is operating on the
output kpatch_elf structure, and thus all symbols are by definition
included.

Remove the check and rename the function since it is redundant.

Signed-off-by: Seth Jennings <sjenning@redhat.com>