msm7x27a-common:libaudio: fix arithmetic on a pointer to void

Change-Id: I0fdc8ee110d6cd6ddda2e84cf8d77ddb6f94183e
msm7x27a-common:libaudio: do not use GNU old-style field designators

Change-Id: I7b2fff73f26bf0e16e8a075333324e2bcab64575