data: Properly access formats in capabilities structure when adding codecs.

Formats within a capabilities structure are addressed starting at 0, not 1.
Assuming 1 causes it to exceed an array.

ASTERISK-24389 #close
Reported by: Kevin Harwell


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/13@424752 f38db490-d61c-443f-a65b-d21fe96a405b