_dsp_init: bring inline with trunk

preparation for clean merge of DTMF TWIST patch

No functional changes, just style.

alecdavis (license 585)
Reported by: Alec Davis
Tested by: alecdavis

related https://reviewboard.asterisk.org/r/2141
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Merged revisions 374365 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 374370 from http://svn.asterisk.org/svn/asterisk/branches/10

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@374379 65c4cc65-6c06-0410-ace0-fbb531ad65f3