refactor new section pair creation

New section pairs are created three times in the current code for
.kpatch.patches, .kpatch.dynrelas, and __mcount_loc.  Each time this is
done, it requires about 40 LOCs.

The commit creates a new helper function, create_section_pair(), to
consolidate this.

Signed-off-by: Seth Jennings <sjenning@redhat.com>