erasure-code isa-l: remove duplicated lines (fix warning)

06a245a added a section def to assembly files; I added it twice to
this file.  There's no damage, but a compiler warning (on machines with
yasm installed)

Signed-off-by: Dan Mick <dan.mick@redhat.com>
Merge pull request #2960 from ceph/wip-10114-fix-warning

erasure-code isa-l: remove duplicated lines (fix warning)

Reviewed-by: Sage Weil <sage@redhat.com>