audioflinger: conform inline ASM to UAL

Summary:
Clang requires some inline ASM to conform to the UAL (Unified Assembler Language).
This fixes a small issue in this inline asm to allow building.

Test Plan: verifying

Reviewers: randall.rushing, anders3408, jriordan001

Reviewed By: randall.rushing

Differential Revision: http://review.codefirex.com/D375
audioflinger: do not use GNU old-style field designators

Summary:
Avoiding the use of GCC extensions improves code portability.
We were building this with GCC still, and missed this in our eradication of GCC extensions.

Test Plan: verified

Reviewers: randall.rushing

Reviewed By: randall.rushing

Differential Revision: http://review.codefirex.com/D374